1. REFRACTION OF LIGHT

2. Refraction is the bending of light as it enters a new medium.
If the new substance is more optically dense the ray bends toward the normal
If its less dense the ray bends away from the normal.

3. Water is Water is Light moves More dense less dense along normal
Oil
air
air
water
glass
water
Bends away from the normal. Speeds up
Moves along normal line. Slows down.
Bends toward the normal. Slows down.

4. Incident angle and refraction angle are measured from the normal line.

5. Absolute Index of refraction
Ratio of the speed of light in a vacuum to the speed of light in the new medium.
Values can be found on the reference table or calculated using:
n = c / v
C = speed of light (m/s)
V = speed in new medium
n = index of refraction
(no units)

6. Sample problem
What is the speed of light as it travels through a bottle of corn oil? (neglect the plastic container)
n=c/v
1.47= 3 x 108m/s V
V = 2.04 x 108m/s

7. Snell’s Law ALSO: n2 / n1 = v1 / v2 = λ1 / λ2
Relates the angle of incidence and angle of refraction to the corresponding indices of refraction.
(incident) (refracted)
n1sinθ1 = n2sinθ2
ALSO: n2 / n1 = v1 / v2 = λ1 / λ2

8. SNELL’S LAW
AIR
LUCITE

9. Sample problem n1sinθ1 = n2sinθ2
Colored light in air is incident on a sample of lucite at an angle of 37˚.
a) What is the angle of refraction?
n1sinθ1 = n2sinθ2
1.0 sin 37 = 1.50 sin θ2
=1.50 sin θ2
sin θ2 = .4012
θ2 = 23.7˚

10. b) What is the velocity of the refracted ray?
n2 / n1 = v1 / v2
1.5 = 3x108m/s V2
v2 = 2.0 x 108m/s

11. c) If the light has a wavelength of 4.8 x 10-7m in
air, what is its wavelength in lucite?
n2 / n1 = λ1 / λ2
1.5 = 4.8 x 10-7m λ2
λ2 = 3.2 x10-7m

12. d) What is the frequency and color of the light? (Use the value for air.)
v = f λ
3x108m/s = f (4.8 x10-7m)
f = 6.25 x 1014Hz
its blue light

13. CRITICAL ANGLE
The incident angle that will cause the light ray to have a refracted angle of 90 degrees
glass
glass
glass
air
air
air
Incident angle is smaller than the critical angle
Incident angle is equal to the critical angle
Incident angle is larger than the critical angle

14. CRITICAL ANGLE SIN θc = 1/n n-index of refraction θc- critical angle
ex: What is the critical angle for lucite?
sin θc = 1/1.50 = 0.66
θc = 41.81˚

15. Refracted light waves