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# 光的折射(上课用)英文版教案

Refraction of light 光的折射

Refraction of light

when the light travels from one medium to another，the direction will be changed，we call this refraction of light．

Why is light refracted?
The speed of light depends on the material through which the light is travelling. When light enters a different material (e.g. when moving from air into glass), the speed of light changes. This causes the light to bend or refract.
air glass

The speed of light is affected by the density of the material through which it is travelling. When light enters a more dense medium, its speed decreases and this is why refraction occurs.

Light from the part of the pencil in the water is refracted as it travels from the water into the air, making it appear bent. How does refraction make this stone look closer to the surface of the water than it really is?

Effects of refraction

Light rays from the stone are refracted as they leave the water.

The brain assumes the rays have travelled in straight lines, and is fooled into forming an image where it thinks the light rays came from.

The archer fish is a predator that shoots jets of water at insects near the surface of the water. The archer fish allows for the refraction of light at the surface of the water when aiming at its prey. The fish does not aim at the refracted image it sees but at a location where it knows the prey to be.
image of prey

Effects of refraction

prey location

Laws of refraction
incidentA ray
normal N

angle of incidence

air
O

water
angle of refraction
N`

C

refracted ray