1. Chapter 14
Refraction

2. Section 14-1
Refraction ~ the bending of a wave as it passes at an angle from one medium into another.
Refraction occurs because of a change in the wave speed.

3. With light, if the speed decreases going from the first to the second material, the ray is bent towards the normal.

4. If the speed increases in the second material, the ray is bent away from the normal.

5. The index of refraction, n, is the ratio of the speed of light in a vacuum (c) to its speed in a given medium (v).
Since c and v are both given in m/s the index of refraction has no units.
The slower the speed, the more optically dense the medium is and the greater n is.

6. Index of Refraction for Various Substances:
Water at 20 degrees C
Ice at 0 degrees C
Air at 0 degrees C
CO2 at 0 degrees

7. Medium 1
Medium 2
Incident Ray
Refracted Ray
Reflected Ray
The relationship between the angles of incidence and refraction is given by Snell’s Law

8. Snell’s Law n1(sin q1) = n2(sin q2)
n1= index of refraction for medium 1
q1 = incident angle
n2 = index of refraction for medium 2
q2 = refracted angle

10. Section 14-1 Practice Problem
A light ray of wavelength 598 nm (produced by a sodium lamp)
traveling through air strikes a smooth, flat slab of crown glass at an angle of 30.0 degrees to the normal. Find the angle of refraction,  r.
Given: q1 = 30 degrees n1 = 1.00
n2 = 1.52
Unknown: q2 = ?
Use the equation for Snell’s Law:
Ni(sin i )= N r (sin  r )
 r = sin-1 [(ni / nr) (sin  i)] = sin=1 [ (1.00 / 1.52) (sin 30 degrees)]
 r = 19.2 degrees