Announcements 11/18/11 Prayer Labs 8, 9 due tomorrow Lab 10 due Tuesday Exam 3 review session: Mon 5-6 pm, room ??? (I’ll

tell you on Monday) Exam 3 starts Monday after break TA office hours: Today 3-5 pm, Monday 6-7 pm

Dilbert

Reading Quiz

What does Rayleigh’s criterion tell us?a. The angle at which both light

polarizations have equal reflection coefficients

b. The angle at which p-polarized light has minimum reflection

c. The angular separation resolvable by an imaging system

d. The number of orders produced by a diffraction grating

Circular Aperture, again

What do you get in this situation?

What if there’s a lens in the hole?

What if there isn’t a board?

What if you have two light sources?

patt

ern

at in

finity

patt

ern

at f

ocus

supe

rimpo

sed

patt

erns

at

focu

s

f

board with hole

Rayleigh: 2nd peak at position of first minimum

Rayleigh Criterion

plotted vs (D/)

Mathematica “FindRoot” command: D/ = 1.21967…

min.resolve 1.22D

(using sin )

Shape of curve involves a “Bessel function” (wait for

some future Physics/Math class)

Rayleigh Criterion

3 slits, equally spaced

Back to 1-D slits, infinitely narrow

(created with parameters so period = 2)

4 slits, equally spaced

Back to 1-D slits, infinitely narrow

5 slits, equally spaced

Back to 1-D slits, infinitely narrow

10 slits, equally spaced

Back to 1-D slits, infinitely narrow

20 slits, equally spaced

Back to 1-D slits, infinitely narrow

100 slits, equally spaced

Back to 1-D slits, infinitely narrow

What have we learned?

The Grating Equation

Where will maxima be?

Resolving PowerN=100

0 .4 0 .2 0 .0 0 .2 0 .4

20

40

60

80

100

120

140

Goes to zero at x=0.0628

= 2/100

width = 1/N separation of

maxima

Resolving Power

Red light vs. Green light

HW 35-6(c): resolving power = / = Nm

Demos

Circular aperture Diffraction grating … with two lasers … with white light source

Reading Quiz

Diffraction of x-rays off of planes of atoms in a crystal is governed by whose law?

a. Bragg’s Lawb. Bohr’s Lawc. Compton’s Lawd. Raman’s Lawe. Thompson’s Law

X-ray Diffraction by Crystals Bragg

equation

http://commons.wikimedia.org/wiki/File:Bragg_diffraction.png

http://l-esperimento-piu-bello-della-fisica.bo.imm.cnr.it/english/history/figuredett2.html

2dsin = m (constructive)

Laue Patterns

http://www.neutronoptics.com/laue.html