Announcements 11/18/11
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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
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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?
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What if there’s a lens in the hole?
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What if there isn’t a board?
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What if you have two light sources?
pattern at infinity
f
superimposed
pattern at focus
patterns at focus
board with hole
Rayleigh: 2nd peak at
position of first minimum
Rayleigh Criterion
Shape of curve
involves a “Bessel
function” (wait for
some future
Physics/Math class)
plotted vs (qD/l)
(using sinq  q)
Mathematica “FindRoot” command: qD/l = 1.21967…
qmin.resolve  1.22
l
D
Rayleigh Criterion
Back to 1-D slits, infinitely narrow
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3 slits, equally spaced
(created with parameters so period = 2p)
Back to 1-D slits, infinitely narrow
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4 slits, equally spaced
Back to 1-D slits, infinitely narrow
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5 slits, equally spaced
Back to 1-D slits, infinitely narrow
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10 slits, equally spaced
Back to 1-D slits, infinitely narrow
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20 slits, equally spaced
Back to 1-D slits, infinitely narrow
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100 slits, equally spaced
What have we learned?
The Grating Equation
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Where will maxima be?
Resolving Power
N=100
Goes to zero at x=0.0628
= 2p/100
width = 1/N 
separation of
maxima
140
120
100
80
60
40
20
0.4
0.2
0.0
0.2
0.4
Resolving Power
Red light vs. Green light
HW 35-6(c): resolving power = l/Dl = Nm
Demos
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Circular aperture
Diffraction grating
… with two lasers
… with white light source
Reading Quiz
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Diffraction of x-rays off of planes of atoms in
a crystal is governed by whose law?
a. Bragg’s Law
b. Bohr’s Law
c. Compton’s Law
d. Raman’s Law
e. Thompson’s Law
X-ray Diffraction by Crystals
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Bragg equation
2dsinq = ml (constructive)
http://commons.wikimedia.org/
wiki/File:Bragg_diffraction.png
http://l-esperimento-piu-bello-dellafisica.bo.imm.cnr.it/english/history/figuredett2.html
Laue Patterns
http://www.neutronoptics.com/laue.html