1. Announcements 10/26/12 Prayer Exam 2 going on…3 people taken it so far
Expected time?
Slinkies: Please turn in and cross your name off the sign-out list, if you haven’t yet
Overboard

2. From warmup Extra time on?
(nothing mentioned by more than one student)
Other comments?
Why does it stop at homework 20? How do we see our other scores?

3. From warmup
Huygen's principle as stated in the textbook involves "wave fronts". What is a wave front?
they are the crests of the waves of light
A wave front is a bunch of points having the same phase.

4. Law of reflection illustrated
Credit: next several slides from Dr. Durfee

5. Law of reflection illustrated

6. Law of reflection illustrated

7. Law of reflection illustrated

8. Law of reflection illustrated

9. Law of reflection illustrated

10. Snell’s Law illustrated

11. Snell’s Law illustrated

12. Snell’s Law illustrated

13. From warmup
What does Snell's law have to do with total internal refraction?
(my answer) TIR happens when Snell’s law predicts that a refracted beam is impossible

14. Demo Stokes computer demo: (5:00)

15. Total Internal Reflection
TIR: the equation

16. Demos Blackboard optics TIR in water soluble oil
Laser captured in stream of water
Fiber Optics

18. Clicker question:
If you have a -0.3 dB change, the final intensity is what fraction of the initial intensity? (You’ll need your calculator.)
78%
83%
88%
93%
98%
-0.3 dB  93.3%
-0.2 dB  95.5%
-0.1 dB  97.7%

19. Clicker question:
When we think of all the points on a wave front as little sources of secondary waves in order to calculate what the wave front will look like after propagating some distance, we are using the idea known as...
the Equivalence theorem
Huygen’s Principle
Fermat’s Principle
Newton’s first law of optics
the Wavelet theorem

20. Image credit: Wikipedia
Huygen’s Principle
Image credit: Wikipedia
Each wavefront serves as source of spherical waves
HW 26-5 (extra credit):
“Stare at the picture until you can visualize that the green lines tangent to the circles connect matching wavefronts.”
Construct an accurate picture like this for a specific situation, show graphically that it gives you Snell’s law

21. Huygen’s Principle, cont.
Image credit: Wikipedia
Double-slit_experiment
A wave hits the two slits
Each slit (infinitely narrow) becomes source of spherical waves
The waves from those two sources interfere with each other

22. Credit: the next few slides are from Dr. Durfee
Spherical Waves
Credit: the next few slides are from Dr. Durfee

23. Huygen’s Construction of a Spherical Wave

24. Huygen’s Construction of a Plane Wave