The document discusses three optical illusions involving refraction of light: 1) A pencil placed obliquely in a glass of water appears broken due to the bending of light at the interface between air and water. 2) A coin on a plate disappears from view as a student walks backward, but reappears when water is poured on the plate, due to the refraction of light rays at the air-water interface. 3) Refraction is defined as the deviation of light's path when passing from one medium to another.

2. Place a pencil Obliquely in a glass of
water. How does it appear?
Doesn't it appear broken? What is the reason for this?

3. The reappearing coin
Place a coin on a plate kept on a table.
●Ask a student to walk backward looking at the coin.
●Ask him to stop at the position when the
coin disappears from sight.
●Pour water in small quantities into the plate.
●Does the student see the coin again?
●What is the reason for the reappearance of the coin?
●What happened before pouring water?
●How does the coin reappears when the
water poured into the plate?

4. The light reflected from the coin travels through water
And air to reach our eyes.
What happened before pouring water?
The light travelled only through air to reach our eye.
'Walk backwards till the coin disappears' means walking backwards till the
reflected light rays from the coin do not reach our eyes.
What happens when water is poured into the plate?
Light rays travelling from air to water and from water
to air undergo slight deviation. Thus the light rays reflected
from the coin reach our eyes, thus making it reappear.
This is the reason for the coin appears a little raised
and why it reappears.

5. Refraction
When light travels from one medium to
another, its path undergoes
a deviation. This phenomenon
of light is called refraction.