UNDERSTANDING REFRACTION OF LIGHT

Refraction of Light

1. The figure shows how light ray passes through a glass block. From the diagram,

• The light ray bends towards the normal when it travels from air to glass from a less densemedium to a denser medium.
• The light ray bends away from the normal when it leaves the glass to air from a denser medium to a less dense medium.
• The angle of refraction , r is always smaller than the angle of incidence, i from less dense medium to a denser medium.
• The emergent ray keeps constant direction. 

2. Refraction of light is the bending of a light ray at the boundary from one medium to another.

3. Any substance that a light ray travels through is called a medium.

Direction of refraction

• when the light travels from a less dense medium to a denser medium, the ray is refracted (toward/away from) the normal at point of incidence.
• when the light travels from a more dense medium to a denser medium, the ray is refracted (toward/away from) the normal at point of incidence.  

Snell's law

• - Snell's law state that the ratio at sin i to a sin r is constant.

Phenomena Due to Refraction of Light

Shallow Swimming pools

• A swimming pool that  appears to be shallower than it really is.
• this is because of light ray from the bottom of the pool being refracted away from the normal as it enter the air.

• When the light ray reaches the eye , it appears to come higher  up.
•  So, the pool appears to be shallower.

Bent Object in Water 

• the figure shows the pencil appearing to be bent at the air-water boundary.
• the light ray from the end of the pencil is refracted at the water-air boundary and bends away from the normal.

• The image of the pencil under the water appears to be higher than it really is.
• Thus, the pencil appears bent at the surface.  

A Fish - Eye View

• A fish or a diver can see object above the water surface , but the objects on the shore would appears to be up in the air at different positions as shown in the diagram .
• Refer to refraction of light , a fish sees the image of an object at a position that differs from its true position.

The Twinkling Stars

• Light from the stars travels in straight lines through the vacuum of space.
• The twinkling of stars at night is due to the refraction of light as it passes through the layers pf atmosphere of different densities.