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