Warmup:

1
Warm-up

• What happens to light as it passes from air into
  glass?
• What happens to light as it passes from air into
  water?
• What happens to light as it passes from air into
  a diamond?

2
Reflection Tracing WS

• Questions?

3
Refraction Notes

• Imagine this
• When the Radio Flyer wagon drifts from the smooth
  pavement onto the rough grass, it will change its
  direction. Why?
• It will bend more towards the grassy side
  (towards the normal) because it travels more
  slowly in the grass than on pavement.

4
Refraction Notes

• When light travels from one material to another,
  it behaves the same way that the wagon does.
• When light bends through a material, we call it
  refraction of light.
• Refraction is caused by the fact that light
  travels more slowly as it passes through more
  dense materials (like glass, water, diamonds,
  etc)

5
Refraction Notes

• Index of Refraction (n) tells how slowly light
  travels through a material, compared to the speed
  of light in a vacuum
• n
• Vm is the speed of light in the material.
• Each material has its own index of refraction.
• The value of n is always greater than 1!!!

3108 m/s vm
6
Refraction Notes

• Example The speed of light in water is 2.25108
  m/s. What is the index of refraction of water?
• n 3108 m/s
• 2.25108 m/s
• 1.33
• The index of water is 1.33. The higher the
  number, the more slowly light travels through the
  material.

7
Refraction Notes

• Snells Law allows us to predict the angle that
  light will bend as it travels into or out of a
  material
• n sin (?i)
• sin (?r)
• ?i is the angle of incidence (to the normal)
• ?r is the angle of refraction (to the normal)

8
Refraction Notes

• Example When light travels into water at an
  incident angle of 45º, it refracts at an angle of
  32º. What is the index of refraction of water?
• n sin (45º)
• sin (32º)

.707 .530
1.33
9
Snells Law Lab

• Get out a piece of paper for the Snells Law Lab.