Chapter 11 – Light, Shadows and Reflection

Page No 113:

Question 1:

Rearrange the boxes given below to make a sentence that helps us understand opaque objects.

Answer:

Opaque objects make shadows.

Page No 114:

Question 2:

Classify the objects or materials given below as opaque, transparent or translucent, luminous or non-luminous:
Air, water, piece of rock, sheet of aluminium, mirror, wooden board, sheet of polythene, CD, smoke, sheet of plane glass, fog, piece of red hot iron, umbrella, lighted florescent tube, wall, sheet of carbon paper, flame of a gas burner, sheet of cardboard, lighted torch, sheet of cellophane, wire mesh, kerosene stove, sun, firefly, moon.

Answer:

Object
Object is Transparent/Translucent/Opaque
Object is Luminous/Non-luminous
Air
Transparent
Non-luminous
Water
Transparent
Non-luminous
Piece of rock
Opaque
Non-luminous
Sheet of aluminium
Opaque
Non-luminous
Mirror
Opaque
Non-luminous
Wooden board
Opaque
Non-luminous
Sheet of polythene
Translucent
Non-luminous
CD
Translucent
Non-luminous
Smoke
Translucent
Non-luminous
Sheet of plane glass
Transparent
Non-luminous
Fog
Translucent
Non-luminous
Piece of red hot iron
Opaque
Luminous
Umbrella
Opaque
Non-luminous
Lighted fluorescent tube
Opaque
Luminous
Wall
Opaque
Non-luminous
Sheet of carbon paper
Opaque
Non-luminous
Flame of a gas burner
Translucent
Luminous
Sheet of cardboard
Opaque
Non-luminous
Lighted torch
Opaque
Luminous
Sheet of cellophane
Translucent
Non-luminous
Wire mesh
Translucent
Non-luminous
Kerosene stove
Opaque
Luminous
Sun
Opaque
Luminous
Firefly
Opaque
Luminous
Moon
Opaque
Non-luminous

Question 3:

Can you think of creating a shape that would give a circular shadow if held in one way and a rectangular shadow if held in another way?

Answer:

When a cylinder is held in sunlight, then a circular shadow or a rectangular shadow can be obtained depending on its orientation related to the Sun.
When the top of the cylinder faces the Sun, then the shadow formed is circular. On the other hand, when the side of the cylinder faces the Sun, then the shadow formed is rectangular.

Question 4:

In a completely dark room, if you hold up a mirror in front of you, will you see your reflection in the mirror?

Answer:

An image is formed due to reflection of light by a plane mirror. In a completely dark room, there is no light present in the room. Thus, no reflection of light takes place by the mirror placed in the room. Hence, no image will get formed by a mirror in a completely dark room.

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