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Announcements 10/26/12

Stay updated with exam 2 information, prayer requests, and announcements. Learn about Slinkies and reflection laws. Find out the expected time for exam results and how to check your scores.

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Announcements 10/26/12

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  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) http://stokes.byu.edu/teaching_resources/refract_script_flash.html

  15. Total Internal Reflection • TIR: the equation

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

  17. 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%

  18. 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

  19. Huygen’s Principle • 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 Image credit: Wikipedia

  20. Huygen’s Principle, cont. • 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 Image credit: Wikipedia http://en.wikipedia.org/wiki/ Double-slit_experiment

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

  22. Huygen’s Construction of a Spherical Wave

  23. Huygen’s Construction of a Plane Wave

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