1. Refraction of Light

2. Refraction of Light
Refraction is the bending of light at the boundary of two transparent substances
We sometimes call the transparent substances media
Refraction causes the pencil to appear “bent”
It also causes water to appear more shallow than it actually is

3. Speed of Light in Different Media
When a light ray moves from one medium into another, it changes speed
example: speed of a light ray in water is less than the speed of a light ray in air
The change in speed is what causes the light ray to bend
We can predict what direction the light will bend in by looking at the index of refraction for the two materials

4. Speed of Light in Different Media
Medium
(km/s)
Index of Refraction (n)
air
1.00
ice
1.31
liquid water
1.33
vegetable oil
1.47
glass
1.52
ruby
1.76
diamond
2.42

5. Drawing Ray Diagrams of Refraction
When drawing a ray diagram of refraction, you must include the following:
Incident ray: the light ray travelling through medium 1 toward the boundary
Refracted ray: the light ray travelling away from the boundary through medium 2
Normal: a line perpendicular to the boundary between the two media, located where the incident ray strikes the second medium
Angle of incidence: the angle between the incident ray and the normal
Angle of refraction: the angle between the refracted ray and the normal

6. Drawing Ray Diagrams of Refraction
normal
incident ray
incident ray
medium 1 (ex. air)
medium 2 (ex. water)
angle of
incidence
boundary
angle of
refraction
refracted ray
incident ray

7. Rules of Refraction
The rules of refraction describe what happens to light when it travels from one medium to another
When travelling from a “fast” (lower n value) medium into a “slow” (higher n value) medium, light bends toward the normal.
When travelling from a “slow” (higher n value) medium into a “fast” (lower n value) medium, light bends away from the normal.
The incident ray, refracted ray, and normal all lie in the same plane. The incident ray and the refracted ray are on opposite sides of the boundary between the two media, and on opposite sides of the normal.

8. Phenomena Related to Refraction

9. Apparent Depth
The depth that an object in water appears to be shallow due to the refraction of light.

10. Apparent Depth
Objects in water appear to be closer than what they actually are.
A fish will be deeper in the water than it appears to be.

11. Why??
Your brain projects the light rays backwards in a straight line to create a virtual image in the water.

12. Virtual Images and Apparent Depth
The virtual images projected by our brains are shallower than they actually are….
apparent
vs. actual
depth.

13. Questions: What does refraction mean?
Why does light bend when it travels between two different mediums?
If light travels from a more dense to a less dense medium, will it bend towards or away from the normal? Include a diagram.
If light travels from a less dense to a more dense medium, will it bend towards or away from the normal? Include a diagram.
What do we mean by apparent depth? Why does this occur? Draw a diagram to help explain.