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 meb. Make sure you have a score for “Project 1”, via website

grade reportc. 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. Einsteinb. Fizeauc. Galileod. Roemere. 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”?http://stokes.byu.edu/emwave_flash.html

Medium?

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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 << db. When λ ≈ dc. When λ >> d

lambda = d/10

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Next three slides: image credit to Dr. Durfee

lambda = d/4

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Index of Refraction

Book table

v = c/n

Index of Refraction

Song: Roy G. BivImage: http://en.wikipedia.org/wiki/Dispersion_(optics)

red

Different wavelengths have different speeds!

Different frequencies have different speeds!

v = f

Dispersion!greenblue

( going into material)

inside = vacuum/n

Thought question

Which color of light travels fastest in glass?

a. Redb. Greenc. Blued. 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

2

fast light(smaller n)

slow light(larger n)

Snell’s Law

n1sin1 = n2sin2

1

2

fast light(smaller n)

slow light(larger n)

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Law of Reflection

refl. = 1

1

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

2 1 1 2

1 2 1 2

v v n nrv v n n

2 1

1 2 1 2

2 2v ntv v n n

If near perpendicular (1-D problem)

2R r 2

1T r

For arbitrary angle (these eqns not needed for HW/exam)

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1 1 2 2.

1 1 2 2

cos cos

cos coss polarn n

rn n

1 2 2 1.

1 2 2 1

cos cos

cos cosp polarn n

rn n

1 1.

1 1 2 2

2 cos

cos coss polarn

tn n

1 1.

1 2 2 1

2 cos

cos cosp polarn

tn n

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. topb. bottom

top

bottom

Demos

Reflection/refraction using water-soluble oil

“Blackboard optics”