Announcements 10/27/10

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Announcements 10/27/10  Prayer  Slinky turn-in  Long list of HW changes/corrections/cancelations for the next month— make sure you got this email!!…
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Announcements 10/27/10  Prayer  Slinky turn-in  Long list of HW changes/corrections/cancelations for the next month— make sure you got this email!!  Term projects: a. Make sure you got emailed feedback from me b. Make sure you have a score for “Project 1”, via website grade report c. Can you change topics? Yes, but you need to send me a new proposal.  Exam 2 starts tomorrow, goes through next Thursday a. Covers through tonight’s HW. b. Anyone need “what’s on exam” handout? c. Can bring handwritten 3x5 card (both sides). Just one!  Exam review session tonight, 5:30 – 7 pm. Room: C295 (next door) a. Remember to come with questions: HW problems, worked problems & concepts from class, demos, labs, Exam 1 problems/multiple choice questions, etc. Reading Quiz  Which of the following scientists did not attempt to make a measurement of the speed of light? a. Einstein b. Fizeau c. Galileo d. Roemer e. Michelson (OK, this is not the answer, but I felt his name should be included on the list even though he wasn’t mentioned in today’s reading because he performed the “canonical experiment”) The wave nature of light  Speed of light…how did each of the people on the preceding slide measure it? Advertisement for Phys 471  What is “waving”? http://stokes.byu.edu/emwave_flash.html  Medium? Reading Quiz  A beam of light passes through a hole of diameter d in a metal plate. Under what condition are we allowed to ignore the diffraction or “spreading” of the light? (This is called the ray approximation.) a. When λ d b. When λ ≈ d c. When λ d lambda = d/10 50 100 150 200 250 300 350 400 450 500 50 100 150 200 250 300 350 400 450 500 Next three slides: image credit to Dr. Durfee lambda = d/4 50 100 150 200 250 300 350 400 450 500 50 100 150 200 250 300 350 400 450 500 lambda = d 50 100 150 200 250 300 350 400 450 500 50 100 150 200 250 300 350 400 450 500 Index of Refraction v = c/n  Book table Index of Refraction Different wavelengths have different speeds! v = lf linside = lvacuum/n Different frequencies have different speeds! Dispersion! (l going into material) blue green red Image:  Song: Roy G. Biv http://en.wikipedia.org/wiki /Dispersion_(optics) Thought question  Which color of light travels fastest in glass? a. Red b. Green c. Blue d. Same Absorption  “Lorentz model” “anomalous” index of refraction index of refraction absorption increasing From Peatross & Ware, frequency textbook for Phys 471 (decreasing l) Why is blue light slower through glass than red light?  It’s closer to an absorption region Index of Refraction  Light ray at boundary fast light q1 (smaller n) slow light q2 (larger n) Snell’s Law  n1sinq1 = n2sinq2 fast light q1 (smaller n) slow light q2 (larger n) Advertisement for Phys 442/471 Law of Reflection  qrefl. = q1 fast light q1 qrefl. Reflections occur (smaller n) off of any boundary, not just via mirrors slow light q2 (larger n) When will you have no reflection? Fresnel Coefficients / Fresnel Equations  If near perpendicular (1-D problem) v2  v1 n1  n2 2v2 2n1 r  t  v1  v2 n1  n2 v1  v2 n1  n2 2 2 R r T  1 r Look familiar??  For arbitrary angle (these eqns not needed for HW/exam) n1 cosq1  n2 cosq2 2n1 cosq1 rs polar .  ts polar .  n1 cosq1  n2 cosq2 n1 cosq1  n2 cosq2 n1 cosq2  n2 cosq1 2n1 cosq1 rp polar.  t p polar.  n1 cosq2  n2 cosq1 n1 cosq2  n2 cosq1 Advertisement for Phys 442, Phys 471 Thought question top bottom  I send white light into a prism as shown below (n 1). Will the red part of the “rainbow” be on the top or the bottom of the outgoing fan of light? a. top b. bottom Demos  Reflection/refraction using water-soluble oil  “Blackboard optics”
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