Answer: Option C. -> opaque
:
C
Mirror consists of a silver coating which reflects thelight falling on it. Hence, it does not allow light to pass through it. So, mirror is an opaque object.

Answer: Option C. -> The sharpness is high if the light is from a point source.
:
C
Ashadowis a region where light from a light source is obstructed by an opaque object. When a single point source of light is present, the screen behind has a clear dark region. But, when multiple sources are present, a part of the screen is partially dark, anda part of the screenis completely dark. This causes the formation of blurred shadow.

Answer: Option B. -> By using reflective glasses.
:
B
Strong sources of light, like Sun, emit very intense light which can damage our eyes. In order to look at them, the intensity must be reduced to an appropriate level. This could be achieved by using partially reflective, partially transparent media.
Therefore, reflective glasses can be used to protect our eyes while looking at a strong source of light.

Answer: Option C. ->  a straight line
:
C
A ray of light always travels in a straight line. It always tends to follow the quickest path between two points which is a straight line for a given medium.

Answer: Option B. -> Mirror
:
B
Opaque objectsdo not allow light to pass through.
A mirror is an opaque object since it reflects light and the light cannot pass through the mirror.

Glass, air and water are transparent as they let light pass through them completely.

Answer: Option D. -> Sun
:
D
Luminous objects emit their own light. This light may come to our eyes directly or through reflection by non-luminous objects enabling us to see. Examples of luminous objects are stars, flashlight etc.

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Each Point: 1 Mark
$\begin{array}{cc}\text{Image}& \text{Shadow}\\ \text{(1) It is formed by reflected rays}& \text{It is formed when no light}\text{is allowed to pass through the object}\\ \text{(2) Images can be seen when reflected}\text{light approaches observer’s eye}& \text{No light approaches observer’s eye}\\ \text{(3) Image provides a lot of information}\text{like colour, shape, etc.}& \text{Shadows are vague and}\text{don’t provide any information}\\ \text{(4) Image can be straight or inverted}& \text{Shadow is not inverted}\\ \text{(5) Size is same as that of the object}& \text{Size can be smaller or larger}\end{array}$

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Reflection of light: 1 Mark
Activity: 4 Marks
When light rays hit a highly polished smooth surface like a mirror, it bounces back to the same medium like a ball thrown against a wall. It is called the reflection of light.
Activity to show the reflection of light: Ask 3 of your friends to join this activity. In a dark room or in the night, ask one of your friends to hold the mirror in one corner of the room. You and your other friend stand anywhere in the room. Take a torch and direct beam of light to the mirror that your friend is holding. Adjust the direction of the torch so that some of the beam of light hits on your friend. This activity shows that the light you directed hits the mirror and bounces back to your friend.

A mirror reflecting beam of light

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If 2 Points: 3 Marks
If 3 Points: 5 Marks
(a) The shadow of the pencil will be small in size when the pencil is taken away from the candle and closer to the wall.
(b)The shadow will be big in size when the pencil is taken away from the wall and closer to the candle.
(c)To get the same sized shadow as the pencil, move the pencil to bring it at an equal distance between the wall and the candle.

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All Points: 2 Marks
To see any non-luminous object, we need the following:
1) Source of light
2) An object
3) Eyes
When light emitted from aluminous object falls on a non-luminous object and is reflected, thereflected light reaches our eyes and enables us to see that object.