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. a.The angle at which both light polarizations have equal reflection coefficients b. b.The angle at which p-polarized light has minimum reflection c. c.The angular separation resolvable by an imaging system d. 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? pattern at infinity pattern at focus superimposed patterns at focus f board with hole

Rayleigh: 2 nd peak at position of first minimum

Rayleigh Criterion plotted vs (  D/ ) Mathematica “FindRoot” command:  D/ = … (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 Power N=100 Goes to zero at x= = 2  /100 width = 1/N  separation of maxima

Resolving Power Red light vs. Green light HW 35-6(c): resolving power = /  = N  m

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. a.Bragg’s Law b. b.Bohr’s Law c. c.Compton’s Law d. d.Raman’s Law e. e.Thompson’s Law

X-ray Diffraction by Crystals Bragg equation wiki/File:Bragg_diffraction.png fisica.bo.imm.cnr.it/english/history/figuredett2.html 2dsin  = m (constructive)

Laue Patterns