Frank ICSE Class 9 Physics Solutions

Frank ICSE Solutions for Class 9 Physics – Electricity and Magnetism

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Frank ICSE Solutions for Class 9 Physics – Electricity and Magnetism

PAGE NO: 323
Solution 1:
Positive and negative are the two kind of charges.

Solution 2:
Net charge on an atom is zero.

Solution 3:
10 is the number of electrons present in Na+.

Solution 4:
An atom does not have any net charge while ion is either a positive charge or a negative charged.

Solution 5:
The friction between two bodies when they are rubbed against each other is the reason of electrification.

Solution 6:
A lightening conductor is a device used to protect the large buildings against lightening during a thunderstorm.

Solution 7:
The speed of light is very fast as compared to the speed of sound in air. So, the thunder is seen fast and then we hear the sound of thunderstorm.

Solution 8:
Electroscope is used to determine the nature of the charge and to detect the presence of charge on the body.

Solution 9:
When a positively charged rod is brought near the positively charged cap then , the positive charge on the cap will spread over because of repulsion and some of them will reach to the leaves . Now, the leaves will have the same positive charge , they will repel each other and hence, leaves will diverge.

Solution 10:
The flow of electrons in a particular direction is called direct current.

Solution 11:
The two differences between primary and secondary cell are :

  • Primary cells cannot be charged again while secondary cells can be charged again and again.
  • In primary cells, chemical reaction is irreversible while in secondary cells , chemical reaction is reversible.

Solution 12:
S.I. unit of current is ampere.

Solution 13:
A battery is the made up of multiple cells.

Solution 14:
Current is a scalar quantity.

Solution 15:
Current is defined as the rate of flow of charge.

Solution 16:
A milliampere is bigger than microampere.

Solution 17:
Rheostat is other name of variable resistor.

Solution 18:
A cell and battery are the two sources of current.

Solution 19:
No, voltmeter is not the same as voltameter.

Solution 20:
Ammeter is used to measure the magnitude of current in the circuit.

Solution 21:
Electrons flow inside the metallic conductor and a battery and cell helps in the movement of electrons in it.

Solution 22:
Voltmeter has high resistance than the ammeter.

Solution 23:
An artificial magnet is the magnetized piece of iron or steel.

Solution 24:
Voltmeter is always connected in parallel to the circuit.

Solution 25:
Ammeter is always connected in series in the circuit.

Solution 26:
S.I unit of resistance is ohm.

Solution 27:
The resistance of conductor is 1 ohm when a current of 1 ampere flows through it when the potential difference across it is 1 volt.

Solution 28:
I = Q/t = 0.8/5 = 0.16 Ampere.

Solution 29:
Rheostat is an instrument to control the current in the circuit.

Solution 30:
Horse-shoe magnet is the shape of the magnet. This shape helps in bringing the poles near to each other and make the strong magnet.

Solution 31:
The magnetism acquired by a magnetic material when it is kept near a magnet is called induced magnetism.

Solution 32:
The points of the magnet where attraction appears the maximum are called poles of magnet and they are situated at ends of the magnet.

Solution 33:
The differences between primary and secondary cell are :

  • Primary cells cannot be charged again while secondary cells can be charged again and again.
  • In primary cells, chemical reaction is irreversible while in secondary cells , chemical reaction is reversible.

Solution 34:
A cell is a source of energy which converts the chemical energy into electrical energy. The cell consists of two electrodes in the form of conducting rod immersed in the solution called electrolyte.

Solution 35:
I = Q/t = n e/t
So, n = I.t / e = 1. 1 / 1.6 x 10-19 = 6.25 x 1018
So, 6.25 x 1018 will be the number of electrons.

Solution 36:
Q = I.t = 4.5 x 2.5 = 11.25 C.

Solution 37:
A key is used to put the current on and off in the circuit.

Solution 38:
The effect to rate of flow of current by the wire is called its electrical reistance. Its S.I unit is ohm.

Solution 39:
The resistance of the wire depends on the following factors :

  • Length of the wire
  • Cross-section of the wire
  • Temperature of the wire.
  • Material of the wire.

Solution 40:
With increase in temperature of the wire, the resistance of wire increases.

Solution 41:
The resistance of wire will become 4ohm.

Solution 42:
Variable resistors consist of a resistance track with connections at both ends and a wiper which moves along the track as you turn the spindle. The track may be made from carbon, cermet (ceramic and metal mixture) or a coil of wire (for low resistances). The track is usually rotary but straight track versions, usually called sliders, are also available.
A variable resistance is a device used to change the resistance and hence the current flowing through a circuit; without changing the voltage.
Frank ICSE Solutions for Class 9 Physics - Electricity and Magnetism 1

Solution 43:
Galvanometer is used to detect the direction of current as well as to detect very weak current. Ammeter is used to measure the magnitude of an electric current in the circuit.

Solution 44:
Voltmeter is used to measure the potential difference between two points in the circuit. Voltameter is an instrument for measuring the voltaic electricity passing through it, by its effect in decomposing water or some other chemical compound acting as an electrolyte.

Solution 45:
The magnets (pieces of lodestone) found in nature is called natural magnet. The properties of magnet are :

  • Attractive propery
  • Directive property
  • like poles repel while unlike poles attract.

Solution 46:
Frank ICSE Solutions for Class 9 Physics - Electricity and Magnetism 2

Solution 47:
The mechanism in which magnetism acquired by the magnetic material when kept near a magnet is called magnetic induction. When the magnetic material get magnetized, the pole developed on its side will be opposite to the magnet’s pole taken near to it. So, opposite poles attract each other. So, induction causes attraction.

Solution 48:
We will start drawing the magnetic field of lines from the north pole of magnet. When a small compass is placed at a point near the north pole of the magnet , the needle turns round on its pivot and settle in the fixed direction. At other points away from the pole the needle settles tangent to the drawn field line. By plotting the directions indicated by the needle, we can draw magnetic field of lines.

Solution 49:
Frank ICSE Solutions for Class 9 Physics - Electricity and Magnetism 3

PAGE NO : 324
Solution 50:
The magnetic field of lines are the lines which get formed by joining the poles of the magnet and they are the continuous curves in which tangent drawn to it will give the direction of magnetic field.

Solution 51:
By breaking the magnet into two halves, magnetic strength will always get half.

Solution 52:
By breaking the magnet into two halves, magnetic strength will always get half. So, the raio of magnetic strength will be 1:2.

Solution 53:

  • The charge gained by the B will be positive charge
  • The B will be charged by the charging by contact. The charge on A will spread on B.

Solution 54:
Electroscope is the device used to detect the presence of charge and the nature of charge on the body. The four stages of the charging a gold leaf electroscope by induction are :
(i) Bring a positively charged rod near the cap of an electroscope. The cap will acquire the negative charge on it by induction. The leaves will diverge
(ii) Earth the electroscope by touching the cap will finger.
(iii) Remove the finger and keep the positively charged rod as such.
(iv) Now, take away the rod. The leaves will diverge because of charges induced by induction.
Frank ICSE Solutions for Class 9 Physics - Electricity and Magnetism 4

Solution 55:
Electrostatic induction is the process of charging a body by bringing another charged body near to it. When the X will come near to body B, the opposite charge will be acquired by body B. So, negative charge will be acquired. Similarly, by electrostatic induction, A will acquire the opposite charge of B so A will acquire the positive charge.

Solution 56:

  1. Lightening conductor is a device used to safeguard the large buildings against lightening of thunderstorm. Normally, they are fitted on the top of tall buildings as a safety device. It consist of few metal spikes fitted to the highest part of building and connected to thick copper strip which is buried inside the earth .
    • Resistance of the conductor: It is the property of the conductor by virtue of which it obstructs the flow of current in the circuit.
    • Potential Difference: It is defined as the amount of work done in moving a charge from one point to another .
    • Open Circuit: In the circuit, if the switch is off or the wire is cut then flow of current in circuit stops and we say that its an open circuit.
    • Closed Circuit: The circuit in which current flows without any obstruction then it’s a closed circuit.

Solution 57:

  • When two bulbs will connect in series then resistance of the circuit will increase so the brightness of the bulbs will decrease.
  • When the two bulbs will be connected in parallel then resistance of circuit will decrease so the bulbs brightness will increase.

Solution 58:

  1. Differences between Conductor and insulators::
    • Conductors allow passing of electric current through it. Insulator does not allow passing of current through it.
    • Silver, Gold are good examples of conductor of electricity. Rubber, Cotton are good examples of insulators.
  2. Flow of electrons is the flow of negative charges inside the conductor while flow of conventional current is the flow of positive charges inside a conductor.
  3. Primary cells are the cells in which chemical reaction is irreversible so they can’t be charged again and again. While , secondary cells are the cells in which chemical reaction is reversible and can be charged again and again.

Solution 59:

  1. Following are the properties of magnet
    • Like poles of magnet repel each other while unlike poles attract.
    • Magnet have an attractive property means it attract the magnetic material towards it.
    • Magnet have the directive property means when it is held freely , it always point towards north-south direction.
  2. The Laws of Magnetism: Like poles repel each other and unlike poles attract each other.
    • Magnetic materials get attracted towards the magnet but non-magnetic materials does not get attracted towards the magnet.
    • Natural magnets are the pieces of lodestone which are found in nature while artificial magnet is the magnetized piece of iron or steel.
    • Iron has high susceptibility and low retentivity means it acquires the magnetism faster and removes it soon as well. While , steel has low susceptibility and high retentivity.

Solution 60:
Frank ICSE Solutions for Class 9 Physics - Electricity and Magnetism 5

PAGE NO : 325
Solution 61:

 

  1. Magnetic induction is the process in which magnetism is acquired by the magnetic material when a magnet is brought near it.
    • If we had a magnet then we will bring the magnet near to steel , if there is force of repulsion or attraction is experienced then steel was magnetized otherwise not.
    • We will held the steel freely, if it points to north-south direction only then it is magnetized otherwise not.
    • Magnetic Meridian: It is the vertical plane containing the magnetic axis of a freely suspended magnet at rest under the earth’s field.
    • Geographic Meridian: It is the vertical plane containing the geographic north and south poles of the earth and passing through the given place in the surface of earth.
    • Angle of declination: The angle between geographic and magnetic meridian is called angle of declination.
    • Angle of Dip: The angle between the horizontal and earth’s magnetic field is known as angle of dip.

Solution 62:

  • When a nylon shirt , blouse or stocking s are removed then they get rubbed with the hairs and due to friction between hairs and nylon, charges get induced on them and attractive force get induced between them.
  • The rubbed ebonite rod contains more electrons so it acquires the negative charge so a charged is acquired by it. But, in the rubbed metal rod , electrons are transferred but through hands and body they pass to the earth so no charges will be there while metal rod is held in hand.
  • Soft iron is used to make electromagnets because it has high susceptibility and low retentivity , it get magnetized very faster and loses magnetism as soon as the inducing magnet is removed.
  • Two steel needles hanging from the lower end of the vertical bar magnet do not hang vertical but will diverge because they got the like poles on it and like poles repel each other so they diverge.
  • If magnetic material is brought near to the magnet then it get attracted although its not magnetized but the magnetic material will be repelled only in case it is magnetised. So repulsion is the sure test of magnetism.

Solution 63:
Frank ICSE Solutions for Class 9 Physics - Electricity and Magnetism 6

Solution 64:
Disadvantages of setting up large dams for hydro-electricity power station::

  • It leads to large catchment area being submerged
  • displacement of people from their places.

Solution 65:
Improved practices in the use of energy :

  • Use the improved cook stove which will save the bio-mass energy
  • Use the improved solar panels and solar furnaces.

Solution 66:
The functions of bureau of energy efficiency setup are :

  • control and keep an eye on consumption pattern
  • develop appliances suitable for the energy change
  • organize posters and slogans for developing awareness in society.

Solution 67:

  • At School: Use of solar cells to light up the electricity in schools and do rain water harvesting, keep the electrical appliances off after the needed period of time.
  • At Home: Use of bio energy for cooking and lightening, use CFLs instead of filament bulbs, keep the electrical appliances off after the needed period of time.

Solution 68:
Frank ICSE Solutions for Class 9 Physics - Electricity and Magnetism 7
Frank ICSE Solutions for Class 9 Physics - Electricity and Magnetism 8

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Frank ICSE Solutions for Class 9 Physics – Electricity and Magnetism: Magnestism

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Frank ICSE Solutions for Class 9 Physics – Electricity and Magnetism: Magnestism

PAGE NO: 320
Solution 1:
Natural magnet is the deposits of the iron ore which has the attracting property of iron The properties of natural magnet are :

  • The magnet has the directive property, when it is suspended freely , it always come in north-south direction.
  • A magnet attracts magnetic substances like iron, steel etc. so, it has the attractive poperty.
  • Like poles repels each other while unlike poles attract each other in magnet.

Solution 2:
Artificial magnets are the magnets which are formed by bringing the natural magnet near it The artificial magnets have the high retentivity means they remains magnetized for the long period of time and that is why they are used for making strong electromagnets.

Solution 3:
The magnetic forces appear to be concentrated at the near ends of the magnet. These points are called the magnetic poles.

Solution 4:
Bring the rod near the magnet, iron rod will get attract towards the magnet while copper will not.

Solution 5:
Suspend a magnet freely; it will always point towards the north -south direction. The pole of the magnet which point towards the north is called north pole and the pole which point towards south is called south pole.

Solution 6:
Magnetic axis: The imaginary line joining the poles of the magnet is called magnetic axis.
Poles of the Magnet: The points of the magnet where the attraction appears to be maximum are called poles of the magnet.
Effective Length of the magnet: The distance between the poles of magnet is the effective length of magnet.

Solution 7:
Suspend the iron bar and magnet freely in the space by using thread. And, move them here and there few number of times. The bar which always points in north south direction after coming to rest is a magnet and other bar is the iron bar.

Solution 8:
No, we cannot isolate the poles of the magnet.

Solution 9:
The magnetism acquired by the magnetic material when it is kept near the magnet is called induced magnetism.

Solution 10:
The lines of the magnetic field are the continuous curve such that the tangent drawn at any point gives the direction of magnetic field at that point.

Solution 11:
The natural magnet which was used for the navigation by the mariners is called lodestone.

Solution 12:
Magnetic compass is used to draw the magnetic field of lines around the magnet.

Solution 13:
No, Magnetic field of lines cannot intersect each other.

Solution 14:
Frank ICSE Solutions for Class 9 Physics - Electricity and Magnetism Magnestism 1

Solution 15:
The simple experiment to show that like poles repel while unlike poles attract each other is : Suspend a bar magnet and allow it to freely rotate. When it will come to rest, it will point towards the north south direction. Now, bring the N pole of second magnet near the North pole of the suspended magnet , we will see repulsion between the two magnets. But, if we bring south pole of second magnet near the north pole of suspended magnet then we will observe attraction. So, we can say like poles repel while unlike poles attract.

Solution 16:
The directions indicated by the needle of compass will help to draw the magnetic lines of force.

Solution 17:
Neutral points are the points where the magnetic field of magnet has the magnitude equal to the magnitude of earth’s magnetic field but in opposite direction.

Solution 18:
Neutral points help in finding the magnitude and direction of earth’s magnetic field at that particular point.

Solution 19:
The resultant magnetic field at neutral point is zero.

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Frank ICSE Solutions for Class 9 Physics – Electricity and Magnetism: Current Electricity

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Frank ICSE Solutions for Class 9 Physics – Electricity and Magnetism: Current Electricity

PAGE NO: 312
Solution 1:
The flow of electrons in a particular direction in a conductor is called an electric current.

Solution 2:
An electric cell is the source of electric current in which chemical energy changes to electrical energy.

Solution 3:
The charge on an electron is -1.6 x 10-19 C.

Solution 4:
The constituents of cell are two electrodes in the form of conducting rods immersed in the solution called electrolyte.

Solution 5:

  • S. I unit of electric current is Ampere
  • S.I unit of potential difference is volt.
  • S.I unit of resistance is ohm.

Solution 6:
I = 1A
T = 1s.
I = Q/t = ne/t
So, n = I.t/e = 1.1/(1.6 x 10-19) = 6.25 x 1018 electrons.

Solution 7:
I = Q/t = 0.7 / 7 = 0.1 Ampere.

Solution 8:
Rheostat is used to control the current in the circuit.

PAGE NO : 313
Solution 9:
Rheostat is the variable name of electrical resistance.

Solution 10:
Switch is used to put the current on and off in the circuit.

Solution 11:
Frank ICSE Solutions for Class 9 Physics - Electricity and Magnetism Current Electricity 1

Solution 12:
I = Q/ t So, Q = I.t = 1.2 x 3.0 = 3.6 C.

Solution 13:
A – is a voltmeter to measure the potential difference, B is an electric resistance to control the current in the circuit , C is the ammeter to measure the magnitude of an electric current, D is cell to provide electric current in circuit, E is an electric key to on and off the circuit, F is the rheostat to control the current in circuit.

Solution 14:
The slope of the graph represents that with current flowing through a conductor is directly proportional to the potential difference applied the resistance of conductor is constant.

Solution 15:
Potential difference between two conductors is defined as the amount of work done in moving the unit positive charge from one conductor to another through the wire.

Solution 16:
Yes, electric current is a scalar quantity.

Solution 17:
The electric resistance of the wire depends on the following factors :

  • The length of the wire.
  • The area of cross-section of the wire.
  • The temperature of the wire.
  • The material of the wire.

Solution 18:
The S.I unit of resistance is ohm.

Solution 19:
If another bulb is connected in series then the resistance of the wire will increase.
If another bulb is connected in parallel then resistance will decrease.

Solution 20:
V = IR.

Solution 21:
The resistance of the wire is 2 ohms if a current of 1 ampere flows through it when the potential difference across it is 2 volt.

Solution 22:
The current I = V/R = 14/28 = 0.5 Ampere.

Solution 23:
The factors on which resistance of the wire depends are:

  • The length of the wire , resistance is directly proportional to the length of wire.
  • The cross-section of the wire , resistance is inversely proportional to the cross-section of the wire.
  • The temperature of the wire , resistance of wire is directly proportional to the temperature of the wire.
  • The material of the wire (good conductors possess less resistance.)

Solution 24:
W = V.Q = 6.3 = 18 Joule.

Solution 25:
The resistance of the conductor is the property due to which it opposes the flow of current in it.

Solution 26:
The potential difference between two points is 1 volt if the work done in transferring 1 coulomb of charge from one point to another point is 1 joule.

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Frank ICSE Solutions for Class 9 Physics – Electricity and Magnetism: Static Electricity

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Frank ICSE Solutions for Class 9 Physics – Electricity and Magnetism: Static Electricity

PAGE NO: 300
Solution 1:
Electrostatics is defined as the study of charges at rest.

Solution 2:
Frictional electricity is also known as static electricity.

Solution 3:
Thales of Miletus was the scientist who observed the electric properties of amber.

Solution 4:
There are two kind of charges – positive and negative charge.

Solution 5:
A positively charged body signifies that its nucleus contains more number of protons than electrons.

Solution 6:
A negatively charged body signifies that it contains number of electrons more than number of protons.

Solution 7:
Benjamin Franklin was the scientist who first assigned the algebraic signs to charges.

Solution 8:
When a glass rod is rubbed with silk,the glass rod acquires the positive charge.

Solution 9:
When ebonite rod is rubbed with cat’s fur, the ebonite rod acquires the negative charge.

Solution 10:
The quantization of charge is the property by virtue of which every charge exists only in discrete lumps or packets of some minimum charge.

Solution 11:
Energy other than electric charge is quantized.

Solution 12:
Q = Ne
N = Q/e = 1C / 1.6 x 10-19 = 6.25 x 1018

PAGE NO : 301
Solution 13:
1C is bigger than charge on an electron.

Solution 14:
Q = Ne
The charge on an electron = -1.6 x 10-19
= 100 x 1.6 x 10-19 = 1.6 x 10-17

Solution 15:
Q = Ne
N = Q/ e = -3.6 x 10-18 /1.6 x 10-19 = 22.5
Since, n is not an integral value so this value of charge is not possible because charge is quantized.

Solution 16:
The origin of frictional forces is electrical in nature.

Solution 17:
The cause of charging is the frictional forces between the two bodied when they are rubbed against each other.

Solution 18:
The Sir Williams Gilbert was the scientist who showed two charges and Benjamin Franklin was the scientist who gave name to charges.

Solution 19:
Two differences between charge and mass are ::

  • Electric charge can be positive , negative or zero while mass of the body is strictly positive.
  • Electric charge is quantized while the quantization of mass is not yet established.

Solution 20:
Yes, mass of the body get affected on charging.

Solution 21:
There will be attractive force between the B and C because both carry opposite charges.

Solution 22:
Unlike charges attract each other and like charges repel each other.

Solution 23:
No, the motion of the object does not affect the charge on the body.

Solution 24:
The properties of an electric charge are

  • Electric charges are quantized.
  • Like charges repel each other while unlike charges attract each other.

Solution 25:
Photons can never have charge because charges never exist without rest mass.

Solution 26:
The silk cloth will acquire the charge opposite to the charge of glass rod . So the charge acquired by silk cloth will be = -1.6 x 10-19 C.

Solution 27:
The S.I unit of charge is coulomb.

Solution 28:
The value of charge on an electron = -1.6 x 10-19 C. No, the charge less than charge of an electron is not possible.

Solution 29:
The net charge on an atom is zero.

Solution 30:
The electrons of the outermost orbit of an atom are the free electrons and they easily leave their respective atoms and become free to move inside the solid.

Solution 31:
An ion is an atom which has either gained one or more electrons or which has lost one or more electrons. When an atom’s valence electrons leave their atom and become free to move inside the solid and move to another atom then positive ion is formed. And, the other atom which gain electrons become the negative ion.

Solution 32:

  • On positive ion, there exist a positive charge.
  • On negative ion, there exists a negative charge.

Solution 33:
If the electrified silk cloth or the ebonite rod are brought near to each other then they will repel each other but when electrified silk cloth and glass rod are brought together then they attract each other. The charges on the electrified silk cloth and ebonite rod is negatives while on glass rod , its positive so we can say that like charges repel each other while unlike charges attract each other.

Solution 34:
When the nylon cloth get rubbed with hairs then it acquires the negative charge because few free electrons get transferred from hairs to nylon and they get attracted towards nylon cloth so the hair stands on their end.

Solution 35:
The charge is quantized and Q = ne where n should be only integer . Since Q = -1.8 e where n is not an integer. So, this charge is not possible.

Solution 36:
Frank ICSE Solutions for Class 9 Physics - Electricity and Magnetism Static Electricity 1

Solution 37:
The purpose of an electroscope is to detect the presence of charge on the body and nature of charge (whether its positively charged or negatively charged) on the body.

PAGE NO : 302
Solution 38:
P is a Cap, Q is plug and R is the bottle in the negatively charged gold leaf electroscope. P is a conductor and Q, R is an insulator.

Solution 39:

  • P will have the positive charge
  • Q will have no charge.
  • Cap of the electroscope will have no charge.
  • The gold leaf will have negative charge.
  • The leaf will diverse because like charges repel each other
  • If electroscope is earthed then metal rod will have positive charge.

Solution 40:
Earthing of an electroscope is meant to take the thick copper strip inside the earth so that charges induced from thunderstorm on the metal spikes can move to earth to safeguard buildings from thunderstorm.

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Frank ICSE Solutions for Class 9 Physics – Sound

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Frank ICSE Solutions for Class 9 Physics – Sound

PAGE NO: 286
Solution 1:
Yes, we can hear in the dark room.

Solution 2:
Sound is produced by the vibrating objects.

Solution 3:
Yes, sound is a form of energy.

Solution 4:
No, sound cannot travel through vacuum. It needs a material medium to travel.

Solution 5:
Yes, sound requires a material medium for transmission.

Solution 6:
The speed of sound depends on the following factors: Density of air, Temperature , Humidity in air as well the wind.

Solution 7:
There is no effect on the wavelength and amplitude on the speed of sound.

Solution 8:
Speed of sound at room temperature is 330 m/s

Solution 9:
Yes, the speed of sound is different in different medium.

Solution 10:
No, the speed of sound in the gas is independent on the change in pressure of the gas.

Solution 11:
Frank ICSE Solutions for Class 9 Physics - Sound 1

Solution 12:
Yes, the speed of sound depends on the direction of wind. When wind is blowing in the direction of propagation of sound , the speed of sound increases. But, when wind blows in the direction opposite to that of sound , the speed of sound decreases.

Solution 13:
Ultrasonic are sounds having frequency higher that 20 KHz and not audible to the human being.

Solution 14:
SONAR stands for the “SOund Navigation And Ranging”.

Solution 15:
Ultrasonic sound has higher frequency than infrasonic sound.

Solution 16:
No, we cannot hear the sound produced due to the vibration of second’s pendulum.

Solution 17:
No, SONAR does not make use of infrasonic waves. Instead, it make use of ultrasonic waves.

Solution 18:
Yes, ultrasound in the medium travels faster than the audible sound.

Solution 19:
No, it is not possible to hear the friend’s voice in vacuum because sound needs a material medium to travel.

Solution 20:
The following are the requisites of medium to travel:

  • The medium should possess elasticity so that particles of medium have tendency to come back to their original position after the displacement.
  • The medium should be frictionless so that there should be loss of energy.
  • The medium must possess inertia so that particles of medium have ability to store energy.

Solution 21:
Sound is produced by the vibrating objects. We require a material medium for the propagation of sound because vibrations of object need to get transferred or transmitted from one place to another.

Solution 22:
With increase in temperature of gas, there is increase in speed of gas because increase in temperature decreases the density of gas. And speed of sound is inversely proportional to density of gas. The speed of gas is independent of the pressure of gas.

Solution 23:

  • No, there is no effect of wavelength and amplitude on the speed of sound.
  • With increase in density, there is decrease in the speed of sound in gas.

Solution 24:
Sound is defined as form of energy that produces the sensation of hearing in our ears. The sound travels in medium through energy transfers by wave motion from one place to another. For example , when the prong of the tuning fork vibrate , the waves start moving from one fork to another , the air start getting compressed . The compression is pushed forward. Now, when the fork vibrate in another direction, the air in the immediate neighbor which was compressed, now get rarefied. As a result, a series of compression and rarefactions are produced and sound energy travels in the direction where compression and rarefactions travel.

Solution 25:
The ratio of speed of sound in air to speed of sound in steel is 1/15.

Solution 26:
The distance of observer from the gun = speed of sound x time taken for the explosion = 350 x 2 = 700m

Solution 27:
Yes, light travels faster in air than water. Because, light does not require any medium for their propagation and they are not mechanical waves. The quantities which oscillate in light are mechanical and electric field. And electric and magnetic field decrease with the medium in between them. So, light travels faster in air than water.

Solution 28:
The flash of light reaches earlier than the sound of thunder because the speed of light (its 3 x 108) is much larger than the speed of sound in air (its 330 m/s).

Solution 29:
The sound of 1000 Hz frequency will be audible to us. Others 2Hz is infrasonic sound frequency and 200 KHz, 8 MHz is ultrasonic sound frequency.

Solution 30:
Frank ICSE Solutions for Class 9 Physics - Sound 2

Solution 31:
There is no atmosphere on moon. So, we cannot hear each other on moon because sound needs a material medium to travel from one place to another. No kind of sound can be heard.

Solution 32:
The following are the three characteristics of the medium required for the propagation of sound:

  • The medium must possess elasticity so that the particles of medium have the tendency to return back to their original positions.
  • The medium must be frictionless so that there is no loss of energy during transmission.
  • The medium must possess inertia such that the particles of medium have the ability to store energy.

Solution 33:
The simple experiment that a person can do to calculate the speed of sound in air is that a person stands at a known distance (d meter) from the cliff and fires a pistol and simultaneously start the stop watch. He stops the stop-watch as soon as he hears a echo. The distance travelled by the sound during the time (t) seconds is 2d.
So, speed of sound = distance travelled / time taken = 2d/t

Solution 34:
Ultrasonics sound is the sound having frequency more than 20KHz. The application of ultrasonic sound is as follows:

  • It is used to detect the flaws in metal casting of automobile tyres.
  • Used in hospitals to detect defects in certain parts of body.

Solution 35:
Sound waves are produced by the object motion back and forth in the medium. Due to which it compresses the medium and compression waves are moved forward. The sound travels in medium through energy transfers by wave motion from one place to another. For example , when the prong of the tuning fork vibrate , the waves start moving from one fork to another , the air start getting compressed . The compression is pushed forward. Now, when the fork vibrate in another direction, the air in the immediate neighbor which was compressed, now get rarefied. As a result, a series of compression and rarefactions are produced and sound energy travels in the direction where compression and rarefactions travel.

Solution 36:
Light waves are electromagnetic waves while the sound waves are mechanical waves. Light waves do not require any material medium for their propagation while sound waves need the material medium for its travel from one place to another.
Due to large magnitude of difference between speed of light (i.e 3 x 108 m/s) to the speed of sound in air (330 m/s) , the light reaches first and then the sound from the object. Like, in thunderstorm, the light reaches first to earth and then person hears the sound of light.

Solution 37:

  • Pressure of air: The speed of sound in air is independent of pressure of air.
  • Temperature of Air: Speed of sound in air is directly proportional to the temperature of air. As the temperature of air increases, the density of air decreases and hence speed of sound increases.
  • Humidity: The speed of sound increases with increase in humidity. The increase of moisture decreases the density of the atmosphere and therefore sound travels faster in moist air.
  • Wind: The speed of sound depends on the direction of wind. When the wind is blowing in the direction of propagation of sound, the speed of sound increases. But, when the wind blows in the direction opposite to that of the sound, the speed of sound decreases.

Solution 38:

  • The bat during its flight at night: Bats emits its own distinctive sounds. The echoes of the sound helps bat to navigate and to locate their prey during night.
  • The dolphin to locate small fish as its prey: Dolphins sends the sound having frequencies between 120 KHz to 150KHz. The returning echoes used to help their preys.

Solution 39:
A person hearing at one end of the long metal bar hears two distinct sounds when the other end is struck with a stone because sound comes from the metal bar as well as from air. The sound travels faster in solids than air. So, first sound comes from metal bar hitting and then from air.

PhysicsChemistryBiologyMaths

Frank ICSE Solutions for Class 9 Physics – Sound: Range of Hearing

by

Frank ICSE Solutions for Class 9 Physics – Sound: Range of Hearing

PAGE NO: 284
Solution 1:
The frequency of sound is defined as the number of vibrations produced by the sound producing object per second.

Solution 2:
S.I unit of frequency is hertz.

Solution 3:
One hertz is defined as one vibration produced in one second by sound producing object.

Solution 4:
The audible range of frequency is 20Hz to 20KHz.

Solution 5:

  • Less than 20Hz – we cannot hear sound.
  • More than 20KHz – we cannot hear sound.

Solution 6:
No, the audible range of frequency does not vary from person to person and also with age of person.

Solution 7:
Sound having frequency less than 20Hz is called infrasonic sound. Sound having frequency greater than 20KHz is called ultrasonic sound.

Solution 8:
The energy carried by ultrasonic sound is very high.

Solution 9:
Applications of Ultrasonic sound

  • Ultrasonic sound is used to detect the flaws in metal castings of automobile tyres.
  • It is used in hospitals to detect defects in certain parts of body.

Solution 10:
Echocardiography is used to obtain the image of the heart by the used of ultrasonic waves.

Solution 11:
SONAR stands for Sound Navigation and Ranging. Sonar helps the oceanographers and ship captains to determine the depth of the ocean.

Solution 12:
Bats emit the high frequencies that range between 20 KHz to 75 KHz. The echoes from these sounds help in locating the obstacles in their path and to avoid them.

Solution 13:
The elephants and whales produce the sound of frequency less than 20Hz. (means infrasonic sounds)

Solution 14:
No, all animals does not have same range of audible frequencies.

Solution 15:
When the sound strike any object and reflect back, the hearing of reflected sound is called echo.

Solution 16:
Echolocation is defined as sending out sounds to judge the location, size and motion of objects from the returning echoes. The animals use this phenomenon to locate the obstacles in their path and avoid them so it helps them in navigation and to locate their prey.

Solution 17:
Three Important uses of echolocation:

  • It helps animals to communicate with each other. e.g dolphins use the echolocation to communicate with other dolphins.
  • It helps in navigation and to locate their prey.
  • It is used by them to hunt for the meal.

Solution 18:
A hearing aid is the device which increases the loudness and intensity of the incoming sound.

Solution 19:
The main components of hearing aid are microphone , amplifier and earphone.

Solution 20:
A ship sends ultrasonic waves downward in the ocean. When the sound waves reaches the ocean floor, they are reflected back to the ship . The time it takes for the signal to return is used to calculate the depth of submerged ship in the ocean.

Solution 21:
High Power, High Energy and good directionality are the properties of ultrasonic sounds which makes them useful.

Solution 22:

  • 10 Hz – Infrasonic sound.
  • 200 Hz – audible sound.
  • 2000 Hz – Audible sound.
  • 45 KHz – Ultrasonic sound

PhysicsChemistryBiologyMaths

Frank ICSE Solutions for Class 9 Physics – Sound: Production and Propagation of Sound

by

Frank ICSE Solutions for Class 9 Physics – Sound: Production and Propagation of Sound

PAGE NO: 278
Solution 1:
Yes, Sound is form of energy.

Solution 2:
Sound is produced by the vibrating objects.

Solution 3:
No, sound cannot travel through vacuum.

Solution 4:
Yes, sound can propagate through solids and liquids.

Solution 5:
No, sound cannot be produced in vacuum. It needs a material medium.

Solution 6:
Speed of sound depends on the density, pressure, temperature, humidity and Wind.

Solution 7:
330m/s is the value of speed in air at N.T.P

Solution 8:
In water, speed of sound is 4.5 times more than that in air. And, in iron, the speed of sound is 15 times as fast in air.

Solution 9:
The speed of sound is more in the humid air as compared to dry air. Because, the air moisture decreases the density of air and speed of sound is inversely proportional to density of air. So, sound travels faster in humid air.

Solution 10:
Speed of sound does not depend on the amplitude and wavelength.

Solution 11:
The sound produced by the moving wheels of the train travels faster on the iron track than in the air. So, firstly sound produced because of railway track is heard and then heard in the air.

Solution 12:
The waves in the air causes sound . Through waves , energy get transferred from one place to another and hence the sound.

Solution 13:
The ratio of speed of light to the speed of sound is 9.1 x 105.

Solution 14:
Speed of sound in air is independent of variation of pressure.

Solution 15:
The speed of sound in air increases with increase in temperature because with increase in temperature, the density of air gases decreases and speed of air is inversely proportional to density of air.

Solution 16:
The diver will hear the sound first because the sound travels faster in water than in air.

Solution 17:
The simple experiment that a person can do to calculate the speed of sound in air is that a person stands at a known distance (d meter) from the cliff and fires a pistol and simultaneously start the stop watch. He stops the stop-watch as soon as he hears a echo. The distance travelled by the sound during the time (t) seconds is 2d.
So, speed of sound = distance travelled / time taken = 2d/t

Solution 18:

  • Moisture in Air: The speed of sound increase with increase in humidity because the moisture in air decrease the density of air and speed of air is inversely proportional to density of air. Hence , the sound travels faster in moist air.
  • Pressure in air: Speed of sound is independent of the air pressure.
  • The speed of sound increases with the increase in temperature of the gas.

Solution 19:
The distance of flash from the observer = speed in air x time taken for the first sound to reach 330 x 6 = 1980m

Solution 20:
Distance between boys = speed of sound x time taken to reach sound = 330 x 2.5 = 825m

PhysicsChemistryBiologyMaths

Frank ICSE Solutions for Class 9 Physics – Light

by

Frank ICSE Solutions for Class 9 Physics – Light

PAGE NO: 261
Solution 1:
Convex mirror has a wider field of view.

Solution 2:
Convex mirror always produces an erect image of the object.

Solution 3:
Convex mirror is used in vehicles to see the traffic on rear side.

Solution 4:
We will use convex mirror to see an enlarged image of our face.

Solution 5:
Image of object placed at a long distance in front of a convex mirror is formed at principal focus. Radius of curvature of convex mirror is 20 cm.
Focal length of convex mirror = radius of curvature/2.
Focal length of convex mirror = 20/2 = 10 cm.
So image will form at principal focus 10 cm away from pole.

Solution 6:
Concave mirror can produce real and diminished image of the object.

Solution 7:
The distance of the principal focus from the pole of the mirror is called the focal length of the mirror.

Solution 8:
The mirror having +20 cm as its focal length is a convex mirror because focal length is taken positive only in case of convex mirror.

Solution 9:
The focal length of plane mirror is infinity.

Solution 10:
The mirror having -15 cm as its focal length is a concave mirror because focal length is taken negative only in case of concave mirror.

Solution 11:
Principal axis is the straight line passing through the pole and the centre of curvature.

Solution 12:
Linear magnification is defined as the ratio of the height of the image to the height of the object. It is taken to be positive for an image to be virtual and erect and negative when image is real and inverted.
Magnification = height of image / height of object.

Solution 13:
Pole is the centre of the reflecting surface, in this case spherical mirror.

Solution 14:
Centre of curvature is the centre of the imaginary sphere to which the mirror belongs.

Solution 15:
Three characteristics of light are:-

  • Light waves can travel through vacuum.
  • Light waves are transverse waves.
  • The velocity of light in vacuum is 3 x 108 m/s.

Solution 16:
Three distinctions between light and sound waves are

  • Light waves can travel through vacuum while sound waves cannot.
  • Light waves are transverse waves while sound waves are longitudinal waves.
  • The velocity of light in air is 3 x 108 m/s while the speed of light in air is just about 330 m/s.

Solution 17:

  • When position of object is at infinity, concave mirror forms a point and Real image at Focus point.
  • When position of object is beyond C, concave mirror forms a Diminished, Real and inverted image between F and C.
  • When position of object is at C, concave mirror forms a Magnified, Real and inverted image at C.

Solution 18:
Image formed by a convex mirror is always Diminished, Virtual and Erect.

Solution 19:
Concave mirrors are used in reflecting microscope, in shaving and make up glasses and in ophthalmoscope.

Solution 20:

  • The distance from the pole in the direction of incident ray is taken positive.
  • The distance from the pole in the direction opposite to the incident ray is taken negative.

Solution 21:
Mirror formula is the relation between the focal length f of the mirror, the distance u of the object from the pole of the mirror, and the distance v of the image from the pole.
Mirror formula is
1/v +1/u = 1/f.
Linear magnification is defined as the ratio of the height of the image to the height of the object. It is taken to be positive for an image to be virtual and erect and negative when image is real and inverted.
Magnification = height of image / height of object.

Solution 22:
Mirror formula is the relation between the focal length f of the mirror, the distance u of the object from the pole of the mirror, and the distance v of the image from the pole.
Mirror formula is
1/v +1/u = 1/f.
Size of body = 1.5 m.
Magnification of body = 1.5.
Magnification = height of image / height of object.
Height of image = magnification x height of object.
Height of image = 1.5 x 1.5= 2.25 m.

Solution 23:
Linear magnification is defined as the ratio of the height of the image to the height of the object. It is taken to be positive for an image to be virtual and erect and negative when image is real and inverted.
Magnification produced by concave mirror is:
Magnification = height of image / height of object.
It is a pure ratio and does not have any units.

Solution 24:
Frank ICSE Solutions for Class 9 Physics - Light 1

Solution 25:
A smooth and polished surface causes regular reflection while a rough and unpolished surface causes irregular reflection.

Solution 26:
When rays of light fall on a surface, they are turned back into the same medium in accordance with some definite laws. This process is known as reflection.
Reflection obeys following two laws

  • The incident ray, the reflected ray, and the normal at the point of incidence, all lie in the same plane.
  • The angle of incidence and the angle of reflection are always equal.

Solution 27:
You can distinguish between plane mirror, a concave mirror, and a convex mirror without touching them. When you look into these mirrors by bringing your face close to each mirror, they will produce an image of your face of different types.

  • A plane mirror will produce an image of the same size as your face.
  • A concave mirror will produce a magnified image of your face.
  • A convex mirror will produce Diminished image of your face.

Solution 28:
You can distinguish between a concave mirror and a convex mirror without touching them. When you look into these mirrors by bringing your face close to each mirror, they will produce an image of your face of different types.

  • A concave mirror will produce a magnified image of your face.
  • A convex mirror will produce Diminished image of your face.

PAGE NO : 262
Solution 29:
Frank ICSE Solutions for Class 9 Physics - Light 2

Solution 30:
Uses of concave mirror:

  • Concave mirrors are used in reflecting microscope
  • Concave mirrors are used in shaving and make up glasses.
    Uses of convex mirror: Convex mirrors are used as a rear view mirror in automobiles as it provides a wider view of following traffic.

Solution 31:
We can see the reflection of our face on a polished table top because a regular reflection occurs in case of a polished surface while on a unpolished table top irregular reflection occurs which make image of our face unclear.

Solution 32:

  • The angle of incidence is the angle made by the incident ray with the plane mirror. {FALSE}
    Correct statement is the angle of incidence is the angle made by the incident ray with the normal to the surface of plane mirror.
  • If a ray of light incident on a plane mirror is such that it makes an angle of 30° with the normal, then the angle of reflection is 60°.{FALSE}
    Correct statement is if a ray of light incident on a plane mirror is such that it makes an angle of 30° with the normal, then the angle of reflection is 30°.
  • If the incident ray makes an angle of X° with the normal, then the angle between the incident ray and reflected ray is 2X°. {TRUE}
  • The image formed in a plane mirror is real, erect and same size as that of the object. {FALSE}
    Correct statement is the image formed in a plane mirror is virtual, erect and same size as that of the object.

Solution 33:
Frank ICSE Solutions for Class 9 Physics - Light 3

Solution 34:
Frank ICSE Solutions for Class 9 Physics - Light 4

Solution 35:
The image formed by a plane mirror is erect and virtual. It is a laterally inverted image. The image formed is of the same size as that of the object. Also, the image and the object are equidistant from the mirror.

Solution 36:
Frank ICSE Solutions for Class 9 Physics - Light 5

Solution 37:
Given, distance of boy from the mirror = 3 m

  • Distance of image from mirror = distance of boy from the mirror = 3 m
    Distance between boy and his image = distance of boy from the mirror + distance of image from mirror = 3+3 = 6 m
  • Now, distance of boy from the mirror = 4 m
    Distance of image from mirror = 4 m
    Distance between boy and his image = distance of boy from the mirror + distance of image from mirror = 4+4 = 8m.

Solution 38:
Periscope is used to see over the top of an obstacle. It is also used in submarines for observing for movement of ships. It can be used from the trenches for observing the movement on the surface of earth.

PAGE NO : 263
Solution 39:
Frank ICSE Solutions for Class 9 Physics - Light 6

Solution 40:

  • Pole is the centre of the reflecting surface, in this case spherical mirror.
  • Centre of curvature is the centre of the imaginary sphere to which the mirror belongs
  • Principal focus of a spherical mirror is a point on the principal axis of the mirror, where all the rays travelling parallel to the principal axis and close to it after reflection from the mirror, converge to or appear to diverge from.
  • Principal axis is the straight line passing through the pole and the centre of curvature.
  • Focus of a concave mirror is a point on the principal axis of the mirror, where all the rays travelling parallel to the principal axis and close to it after reflection from the mirror converge to that point.
  • Normal to the surface of a mirror at any point is the straight line at right angle to the tangent drawn at that point.

Solution 41:
Frank ICSE Solutions for Class 9 Physics - Light 7

Solution 42:
Frank ICSE Solutions for Class 9 Physics - Light 8

Solution 43:
Frank ICSE Solutions for Class 9 Physics - Light 9

Solution 44:
Frank ICSE Solutions for Class 9 Physics - Light 10

Solution 45:
Frank ICSE Solutions for Class 9 Physics - Light 11

Solution 46:
Frank ICSE Solutions for Class 9 Physics - Light 12

PAGE NO : 264
Solution 47:
Frank ICSE Solutions for Class 9 Physics - Light 13

Solution 48:
Frank ICSE Solutions for Class 9 Physics - Light 14

Solution 49:
Frank ICSE Solutions for Class 9 Physics - Light 15

Solution 50:
Frank ICSE Solutions for Class 9 Physics - Light 16

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Frank ICSE Solutions for Class 9 Physics – Light: Spherical Mirrors

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Frank ICSE Solutions for Class 9 Physics – Light: Spherical Mirrors

PAGE NO: 258
Solution 1:
A spherical mirror is a part of a hollow glass sphere silvered on one side.

Solution 2:
Frank ICSE Solutions for Class 9 Physics - Light Spherical Mirrors 1

Solution 3:
Focal length = 1/2 of radius of curvature
= 1/2 x 30 = 15cm.

Solution 4:
Focal point is the principal focus of the mirror where a parallel beam of light meets(or appear to meet) after reflection from the mirror.

Solution 5:
Frank ICSE Solutions for Class 9 Physics - Light Spherical Mirrors 2

Solution 6:

  • Pole is the centre of the reflecting surface, in this case spherical mirror.
  • Centre of curvature is the centre of the imaginary sphere to which the mirror belongs
  • Aperture is the distance between the extreme points on the periphery of the mirror.
  • Principal axis is the straight line passing through the pole and the centre of curvature.
  • The principle focus of a spherical mirror may be defined as a point on its principle axis where a beam of light parallel to the principle axis converges to or appears to diverge from after reflection from the spherical mirror.

Solution 7:
Convex mirror has a wider field of view.

Solution 8:
Concave mirrors are used in reflecting microscope, in shaving and make up glasses and in ophthalmoscope.

Solution 9:
Convex mirrors are used as a rear view mirror in automobiles as it provides a wider view of following traffic.

Solution 10:
Convex mirror is used in vehicles to see the traffic following it.

Solution 11:
The relationship between the focal length, f and radius of curvature, r is
f = 1/2 x r.

Solution 12:
Frank ICSE Solutions for Class 9 Physics - Light Spherical Mirrors 3

Solution 13:
Frank ICSE Solutions for Class 9 Physics - Light Spherical Mirrors 4

Solution 14:
Concave mirror can produce real and diminished image of the object.

Solution 15:
The focal length of plane mirror is infinity.

Solution 16:
The object should be placed between F and P to obtain its magnified and erect image.

Solution 17:
Frank ICSE Solutions for Class 9 Physics - Light Spherical Mirrors 5

Solution 18:
Linear magnification is defined as the ratio of the height of the image to the height of the object. It is taken to be positive for an image to be virtual and erect and negative when image is real and inverted.
Magnification = height of image / height of object.

Solution 19:
SI unit of focal length is meter.

Solution 20:
The top mirror is convex mirror, the middle mirror is concave mirror and bottom mirror is a plane mirror.

Solution 21:
The mirror having +15 cm as its focal length is a convex mirror because focal length is taken positive only in case of convex mirror.

Solution 22:
The mirror having -20 cm as its focal length is a concave mirror because focal length is taken negative only in case of concave mirror.

Solution 23:
When we look into a plane mirror, the image of our face is virtual because the image cannot be obtained on a screen.

Solution 24:
When an object is brought towards the concave mirror, the position of the image moves away from the mirror and the size increases and it remains inverted but at object position between F and P, the image is virtual, magnified and erect.

Solution 25:
Frank ICSE Solutions for Class 9 Physics - Light Spherical Mirrors 6

PAGE NO : 259
Solution 26:
Frank ICSE Solutions for Class 9 Physics - Light Spherical Mirrors 7

Solution 27:
Frank ICSE Solutions for Class 9 Physics - Light Spherical Mirrors 8

Solution 28:
Frank ICSE Solutions for Class 9 Physics - Light Spherical Mirrors 9

Solution 29:
Frank ICSE Solutions for Class 9 Physics - Light Spherical Mirrors 10

Solution 30:
Frank ICSE Solutions for Class 9 Physics - Light Spherical Mirrors 11

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Frank ICSE Solutions for Class 9 Physics – Light: Reflection of Light

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Frank ICSE Solutions for Class 9 Physics – Light: Reflection of Light

PAGE NO: 245
Solution 1:
Light may be defined as the radiant energy which produces in us the sensation of sight. Light itself is invisible but makes other objects visible.

Solution 2:
Yes, light is a form of energy that produces the sensation of vision in our eyes.

Solution 3:
The velocity of light in vacuum is 3 x 108 m/s.

Solution 4:
Two sources of light are

  • Natural, for e.g. Sun
  • Artificial, for e.g. Light bulb.

Solution 5:
Four characteristics of light are :-

  • Light waves can travel through vacuum
  • Light waves are transverse waves
  • Wavelength of light waves is short so that their length is measured in centi-microns.
  • The velocity of light in vacuum is 3 x 108 m/s.

Solution 6:
The Sun and the stars are the two luminous bodies.

Solution 7:
Two non -luminous bodies are moon, chair.

Solution 8:
Frank ICSE Solutions for Class 9 Physics - Light Reflection of Light 1

Solution 9:
A ray of light is the path along which light travels.

Solution 10:
Three distinctions between light and sound waves are

  • Light waves can travel through vacuum while sound waves cannot.
  • Light waves are transverse waves while sound waves are longitudinal waves.
  • The velocity of light in air is 3 x 108 m/s while the speed of light in air is just about 330 m/s.

PAGE NO : 246
Solution 11:

  • A ray of light
  • Divergent beam of light
  • Divergent beam of light
  • Parallel beam of light

Solution 12:
The substance through which light is made to pass is called medium.

Solution 13:
Rectilinear propagation of light is that the light travels along a straight line.

Solution 14:
No, glass is a transparent medium.

Solution 15:
No, no metal is transparent by nature.

Solution 16:
Frank ICSE Solutions for Class 9 Physics - Light Reflection of Light 2

Solution 17:
Waxed paper is the translucent medium among the given substances.

Solution 18:
Frank ICSE Solutions for Class 9 Physics - Light Reflection of Light 3

Solution 19:
Two observations that proves that light travels in a straight line are :-

  • Sunlight coming through a hole in a dark room, we can easily see that light travels in a straight line
  • Light coming from a laser light, used for presentation, can also be seen to travel in straight line.

Solution 20:
When rays of light fall on a surface, they are turned back into the same medium in accordance with some definite laws. This process is known as reflection.

Solution 21:
A smooth and polished flat surface is the cause of regular surface.

Solution 22:
Reflection obeys following two laws

  • The incident ray, the reflected ray, and the normal at the point of incidence, all lie in the same plane.
  • The angle of incidence and the angle of reflection are always equal.

Solution 23:
The height of plane mirror should be half of the size of the object to get a full image of the object. So for a man of height 1.6 m tall should use a 0.8m tall plane mirror.

Solution 24:
Rectilinear propagation of light is that the light travels along a straight line.

Solution 25:
Lateral inversion is the reversal of image experienced in a plane mirror. The image is of the same size and equidistant from the object but the left and right sides are transposed.

Solution 26:
Formation of image is the phenomenon based on laws of reflection.

Solution 27:
The principle employed in a periscope is successive reflections from two plane mirrors.

Solution 28:
The point at which the light is incident on the reflecting surface is called the point of incidence.

Solution 29:
Any smooth, highly polished reflecting surface is called mirror.

Solution 30:
A smooth, highly polished plane surface is called plane mirror.

Solution 31:
The angle between the incident ray and the normal to the surface at the point of incidence is called the angle of incidence.

Solution 32:
Frank ICSE Solutions for Class 9 Physics - Light Reflection of Light 4

Solution 33:
Given, angle between incident ray and mirror = 35°

  • Angle of incidence = angle of mirror to the normal – angle between incident ray and mirror
    = 90 – 35 = 55°
  • Angle of reflection = angle of incidence = 55°
  • Total angle turned = angle of incidence + angle of reflection
    = 55 + 55 = 110°
  • The angle between incident ray and reflected ray = Angle of incidence + Angle of reflection
    = 55 + 55 = 110°

Solution 34:
Given, distance of boy from the mirror = 3 m

  • Distance of image from mirror = distance of boy from the mirror = 3 m
    Distance between boy and his image = distance of boy from the mirror + distance of image from mirror = 3+3 = 6 m
  • Now, distance of boy from the mirror = 4 m
    Distance of image from mirror = 4 m
    Distance between boy and his image = distance of boy from the mirror + distance of image from mirror = 4+4 = 8 m.

Solution 35:
Frank ICSE Solutions for Class 9 Physics - Light Reflection of Light 5

PAGE NO : 247
Solution 36:
Two characteristics of image formed by plane mirror are

  • Image is erect and virtual
  • Image and object are of same size.

Solution 37:
Frank ICSE Solutions for Class 9 Physics - Light Reflection of Light 6

Solution 38:
Frank ICSE Solutions for Class 9 Physics - Light Reflection of Light 7

Solution 39:
Frank ICSE Solutions for Class 9 Physics - Light Reflection of Light 8

PhysicsChemistryBiologyMaths

Frank ICSE Solutions for Class 9 Physics – Heat: Transmission of Heat

by

Frank ICSE Solutions for Class 9 Physics – Heat: Transmission of Heat

PAGE NO: 226
Solution 1:
Conduction, convection and radiation are three modes of transfer of heat.

Solution 2:
The process of conduction involves the transmission of heat from the hot end to the cold end from particle to particle of the medium.

Solution 3:
No, conduction is not possible in vacuum.

Solution 4:
Thermal insulation means restriction of transfer of heat by any means.

Solution 5:
Good conductor allow heat to pass through them easily while bad conductor of heat does not allow heat to pass them.

Solution 6:
No, liquids are poor conductors of heat.

Solution 7:

  • Metals are the best conductor of heat.
  • Gases are the worst conductor of heat.

Solution 8:
Among all the metals, Silver is most conducting.

Solution 9:
Air is most non-conducting.

Solution 10:
No, air is not a good conductor of heat.

Solution 11:
Yes, this is a correct statement. Ebonite and asbestos are worst conductor of heat.

Solution 12:
Cooking utensils are made up of metals because metals are good conductors of heat and they easily allow the heat to pass through them.

Solution 13:
Brick is bad conductor of heat, hence bricks greatly reduce the conduction of heat from outside to the room. In order to ensure better insulation, bricks are made hollow so that air filled between these gaps provides insulation to heat.

Solution 14:
Mercury is good conductor of heat.

Solution 15:
In cold countries, windows have two glass panes and a thin layer of air in between these two glass panes because air is a poor conductor of heat; it obstructs the conduction of heat from the room to the outside.

Solution 16:
Order of increasing heat conductivity:
Air < water< mercury < copper.

Solution 17:

  • Water is heated from below because water is heated by process of convection and in process of convection heat always flows in upward direction from downward direction.
  • In process of convection heat is transferred from one point to another by actual movement of particles of medium and as particles of solid cannot move so process of convection is not possible in case of solids.
  • Conduction is not possible in Vacuum because process of conduction require a material medium for transfer of heat.
  • Inside the refrigerator, cooling takes place by convection. The freezing chamber at the top produces cool and heavy air which descends and hot air from below goes up setting convection current. Thus, cooling in a refrigerator is kept near the top.
  • As earth surface gets heated by sun rays and due to process of convection the air near earth surface open to sunlight get heated while in shade sun rays does not fall on earth surface so air near that surface would not heat up.

Solution 18:
Frank ICSE Solutions for Class 9 Physics - Heat Transmission of Heat 1

Solution 19:
Frank ICSE Solutions for Class 9 Physics - Heat Transmission of Heat 2

PAGE NO : 227
Solution 20:
We receive heat from sun by process of Radiation.

Solution 21:
Radiating power of a surface can be increased by blackening it.

Solution 22:
Heat radiation travels with speed of light and always follows straight path.

Solution 23:
The flask consists of a double walled glass container with vacuum between the walls A and B. The inner side of A and the outer side of B are silvered. It has a narrow mouth which is closed by a non-conducting rubber stopper.
If a hot liquid is placed inside the flask, it cannot lose heat by conduction or convection, as there is no air between the walls. The small amount of heat lost from the liquid by radiation is reflected back into the liquid by silvering of the inner wall A and any radiation striking the outer wall B, is reflected back and prevented from reaching the liquid.

Solution 24:
Green house is a glass house constructed to keep delicate and rare plants that require warmth and protection from weather. It is constructed by panels of glass. The temperature in a green house rises because heat enters the house through the glass but cannot escape out, because the glass reflects the heat back to the inside of the house. This makes glass house warmer than the outside environment.

Solution 25:
Take two sheets of tin plates, one blackened and the other is polished brightly. Fix some drawing pins on the outer side of both sheets using wax. Fix these plates vertically at a very short distance apart. Place a Bunsen burner midway between them. When you light the burner you will observe that the pins from the black painted sheet start dropping while the pins on the polished surface remain in the same position for much longer time.
Thus, we can conclude that black surface is better absorber of heat than the polished one.

Solution 26:

  • As convection require medium for transfer of heat so heat loss due to convection can be minimized if the substance is kept away from any material medium.
  • Similarly for conduction, as conduction also require medium for transfer of heat so heat loss due to conduction can be minimized if the substance is kept away from any material medium.
  • Heat loss due to radiation can be minimized by polishing the surface as polished surfaces radiate less heat.

Solution 27:

  • As no material medium surrounds the ball so there is no possibility of losing heat by conduction or convection. The ball will lose heat by Radiation.
  • Ball will lose minimum amount of heat if it is polished.
  • As loss of heat take place by Radiation and process of radiation does not require any material medium, so there is no role of air in loss of heat.

Solution 28:

  • CFC means Chlorofluorocarbons which are produced mainly by refrigeration industries, aerosol cans, coolants, propellants and plastic foams. They cause global warming.
  • UV means ultraviolet range of radiations. These are the radiations which are emitted by sun and they enter our atmosphere.
  • WHO is World Health Organization which put a check on diseases and global warming etc.

Solution 29:
Green house is a glass house constructed to keep delicate and rare plants that require warmth and protection from weather. It is constructed by panels of glass. The temperature in a green house rises because heat enters the house through the glass but cannot escape out, because the glass reflects the heat back to the inside of the house. This makes glass house warmer than the outside environment. This phenomenon is called green house effect.

Solution 30:
Carbon dioxide, Carbon monoxide, methane are green house gases.

Solution 31:
As fossil fuels are non-renewable sources of energy they are not available again and again if are fully exhausted, so they should not be used extensively.

Solution 32:
Global warming occurs due to the presence of carbon di- oxide, CFCs, methane in the atmosphere. Carbon dioxide acts as a transparent gas to incoming shortwave radiations which the earth re-radiates into space. It therefore traps the outgoing longwave radiations thus warming lower atmosphere of the earth thereby causing global warming.

Solution 33:
Harmful effects of global warming are:

  • The atmospheric temperature of earth would increase thereby making it difficult for a living being to survive.
  • It would melt down the polar caps thus increasing the size of the ocean and leading to floods, tsunami, etc.
  • The increase in temperature would affect climate and rainfall thus affecting flora and fauna.
  • Human beings would be vulnerable to diseases as microbes would get warmth to grow.

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Frank ICSE Solutions for Class 9 Physics – Heat: Thermometry

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Frank ICSE Solutions for Class 9 Physics – Heat: Thermometry

PAGE NO: 209
Solution 1:
Temperature is the quantity that tells about the thermal state of a body i.e. the degree of hotness or coldness of a body.

Solution 2:
Thermometer is used for measuring the temperature of a body.

Solution 3:
Thermometer works on the principal that substances expand when heated and contract on cooling.

Solution 4:
Range of thermometer is the range of temperature which can be measured by thermometer.

Solution 5:
Mercury is the liquid used in a clinical thermometer

Solution 6:
The usual range of temperature marked on clinical thermometer is 95° F to 110°F.

Solution 7:
Fahrenheit designed the first thermometer.

Solution 8:
Before constructing a thermometer, we determine lower fixed point and upper fixed point and divide the whole range of thermometer into specific number of equal divisions to provide a scale for measuring the temperatures within a range.

Solution 9:
The clinical thermometer is specially designed thermometer used to measure the temperature of a human body easily and as accurately as possible.

Solution 10:
Three properties of a liquid which make it suitable to be used in a thermometer are:

  • The substance should have high coefficient of expansion so that it is sensitive to the smallest change in temperature
  • The substance should have uniform expansion all over its entire volume
  • The substance should have minimum specific heat so that it absorbs minimum heat from the body under measurement.

Solution 11:
Two disadvantages of using mercury as a thermometric liquid:

  • It does not have uniform expansion.
  • Mercury is less sensitive than alcohol as its coefficient of expansion is less than alcohol.

Solution 12:
Three advantages of using mercury as a thermometric liquid:

  • Mercury is good conductors of heat.
  • Mercury have high coefficient of expansion thus is sensitive to the smallest change in temperature.
  • Freezing points is very low and boiling point is high.

Solution 13:
Water is not used as a thermometric liquid because it has low coefficient of expansion so it is less sensitive to temperature changes. Moreover, it is transparent thus making it difficult to read the thermometer and water evaporates with time thus producing error and also the freezing and boiling points are also low.

Solution 14:
Temperature in Kelvin To K = Temperature in Celsius To C + 273.
To K = 0°C + 273
To K =273 K.

Solution 15:
Body temperature of a healthy person is 98.4oF.
We know C/100 = (F – 32)/180.
C =5/9(F- 32)
C = 5/9(98.4 – 32)
C = 5/9 x 66.4
C =36.88°C
Temperature of body of healthy man is 36.88°C.

Solution 16:
Absolute scale of temperature is Kelvin scale.
Conversion of temperature from Celsius to Kelvin scale is
Temperature in Kelvin To K = Temperature in Celsius To C + 273.
So a rise of temperature of 1°C in Celsius scale is equal to rise of 1°K in Kelvin scale.

Solution 17:
Kelvin temperature scale is used in SI system.

Solution 18:
In Celsius scale there are two fixed points namely lower fixed point and upper fixed point at 0°C and 100°C respectively. This range is divided into 100 equal divisions and each part gives 1°C.

Solution 19:
We know C/100 = (F – 32)/180.
C =5/9(F- 32)
9/5 C + 32 =F
F = 9/5 C + 32.
Temperature given in Celsius = -15°C.
F = 9/5 x (-15) +32
F = -27 +32
F = 5°F.

Solution 20:
Absolute zero of temperature is 0°K.
Temperature in Kelvin To K = Temperature in Celsius To C + 273.
0°K = To C +273.
To C = -273°C.
Absolute zero of temperature on Celsius scale is -273°C.

Solution 21:
Difference of temperature of two bodies in Celsius scale = 1°C.
We know C/100 = (F – 32)/180.
C =5/9(F- 32)
9/5 C + 32 =F
F = 9/5 C + 32.
So, difference of 1° in Celsius scale is equal to the difference of 9/5° in Fahrenheit scale.
Thus, Difference of 1°C of temperature of two bodies in Celsius scale is equal to difference of 1.8° in Fahrenheit scale.

Solution 22:
Celsius invented the Celsius scale of temperature.

Solution 23:
Fahrenheit invented the Fahrenheit scale of temperature.

Solution 24:
Mercury, alcohol are commonly used in thermometers.

PAGE NO : 210
Solution 25:
Camel and are two animals which are able to increase their body temperature in summers and decrease their body temperature in winters.

Solution 26:
CGS unit of heat is Joule denoted by J.
1 J is amount of heat required to raise the temperature of a body by 1/4.12°C of temperature.

Solution 27:
Frank ICSE Solutions for Class 9 Physics - Heat Thermometry 1

Solution 28:
Frank ICSE Solutions for Class 9 Physics - Heat Thermometry 2

Solution 29:
Relation between Celsius and Fahrenheit scales of temperature is
C/100 = (F – 32)/180.

Solution 30:
Temperature of ice point on Fahrenheit scale =32°F.
Temperature of steam point on Fahrenheit scale =212°

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