2. Announcements
Waves Pt 2. Exam on Monday (18 MC, 2 FR)
TC due Tomorrow

3. Bouncing Beams and Sticky Glass 5.2.2 Reflection/Refraction

4. Reflection
Equation
normal
incident
ray
reflected
ray θi θr
Waves that change mediums or hit boundaries obey the Law of Reflection.
Angles are always measured from the normal!

6. Refraction: Quick Summary

7. Refraction Equation Snell’s Law
incident
ray
normal
θi or θ1
reflected
ray θr
Less dense  More dense = toward normal
More dense  Less dense = away from normal
* Change in speed* n1 n2 θ2
refracted
ray

9. Note: This is why you see your reflection when you look out a window

12. Answer: Choice 1

13. Refraction (Special Cases)
Special cases in which no bending occurs…
Two mediums with the same index of refraction.
A ray entering another medium at an angle of 0°
n1sinθ1 = n2sinθ2
1.47 sinθ1 = 1.47 sinθ2
θ1 = θ2
corn oil
glycerol
n1sinθ1 = n2sinθ2
1.0 sin 0° = 2.42 sinθ2
0 = 2.42 sinθ2
θ2 = 0°
air
diamond

14. air is faster (lower index)
Example
A ray of light with a frequency of 5.09 x 1014 hertz moves from air into flint glass. The angle with which the ray strikes the surface of the flint glass is 40° away from the normal. Which is the faster medium? Determine the angle of refraction. Draw the refracted ray.
air is faster (lower index)
n1sinθ1 = n2sinθ2
1.00 sin 40° = 1.66 sinθ2
θ2 = 23°
air
flint
glass