Announcements 10/26/11 Prayer Slinkies: Please turn-in, and cross your name off of

the sign out list. Exam 2 starts tomorrow, goes through Tuesday

eveninga. Covers through tonight’s HW (HW 24)b. Like last time, no notes allowed, but I give you

equations Comment from Chris: when turning in multiple

assignments, staple them separately. Found a white sweater after review session last night.

Overboard

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”)

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How did they all attempt to measure it?

xkcd

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The wave nature of light

What is “waving”?http://stokes.byu.edu/emwave_flash.html

Medium?

Polarization: quick definition

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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lambda = d

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Index of Refraction

Book table

v = c/n

Index of Refraction

Song: Roy G. Biv (start at 0:30)http://www.youtube.com/watch?v=Gf33ueRXMzQ

Image: http://en.wikipedia.org/wiki/Dispersion_(optics)

red

Different wavelengths have different speeds!

Different wave-lengths (k values) 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 oscillator 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 “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”