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

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

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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

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