Announcements 10/27/10 Prayer Slinky turn-in Long list of HW changes/corrections/cancelations for the next month— make sure you got this !! Term projects: a. a.Make sure you got ed feedback from me b. b.Make sure you have a score for “Project 1”, via website grade report c. c.Can you change topics? Yes, but you need to send me a new proposal. Exam 2 starts tomorrow, goes through next Thursday a. a.Covers through tonight’s HW. b. b.Anyone need “what’s on exam” handout? c. c.Can bring handwritten 3x5 card (both sides). Just one! Exam review session tonight, 5:30 – 7 pm. Room: C295 (next door) a. 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. a.Einstein b. b.Fizeau c. c.Galileo d. d.Roemer e. 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? What is “waving”? Medium? Advertisement for Phys 471

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. a.When λ << d b. b.When λ ≈ d c. c.When λ >> d

Next three slides: image credit to Dr. Durfee

Index of Refraction Book table v = c/n

Index of Refraction Song: Roy G. Biv Image: /Dispersion_(optics) /Dispersion_(optics) red Different wavelengths have different speeds! Different frequencies have different speeds! v = f Dispersion! green blue ( going into material) inside = vacuum /n

Thought question Which color of light travels fastest in glass? a. a.Red b. b.Green c. c.Blue d. d.Same

Absorption “Lorentz model” From Peatross & Ware, textbook for Phys 471 absorption index of refraction increasing frequency (decreasing ) “anomalous” index of refraction Why is blue light slower through glass than red light?  It’s closer to an absorption region

Index of Refraction Light ray at boundary 11 22 fast light (smaller n) slow light (larger n)

Snell’s Law n 1 sin  1 = n 2 sin  2 11 22 fast light (smaller n) slow light (larger n) Advertisement for Phys 442/471

Law of Reflection  refl. =  1 11 22 fast light (smaller n) slow light (larger n)  refl. Reflections occur off of any boundary, not just via mirrors When will you have no reflection?

Fresnel Coefficients / Fresnel Equations If near perpendicular (1-D problem) For arbitrary angle (these eqns not needed for HW/exam) Advertisement for Phys 442, Phys 471 Look familiar??

Thought question 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. a.top b. b.bottom top bottom

Demos Reflection/refraction using water-soluble oil “Blackboard optics”