1. Announcements 3/23/12 Prayer
Handouts from last time: Bessel function (for next lecture), and exam 3 review
Yesterday’s lab: worked until early afternoon…
xkcd

2. Reading Quiz
The array theorem and the book’s treatment of diffraction gratings are for the __________ approximation.
Fresnel
Fraunhofer

3. Reading Quiz The array theorem applies to: small circular holes only
narrow slits only
any identical apertures

4. Fourier Transform of shifted function

5. Array Theorem

6. Reading Quiz
The resolving power of a spectrometer, l/Dl, depends on the:
number of slits illuminated on the grating
separation between slits of the grating
both of the above

7. Diffraction Grating
“Fraunhofer n-slit” animation

8. 1-D slits, infinitely narrow
3 slits, equally spaced
(created with parameters so period = 2p)

9. Back to 1-D slits, infinitely narrow
4 slits, equally spaced

10. Back to 1-D slits, infinitely narrow
5 slits, equally spaced

11. Back to 1-D slits, infinitely narrow
10 slits, equally spaced

12. Back to 1-D slits, infinitely narrow
20 slits, equally spaced

13. Back to 1-D slits, infinitely narrow
100 slits, equally spaced
What have we learned?

14. The Grating Equation
Where will maxima be?

15. Red light vs. Green light
Spectrometer
Red light vs. Green light

16. width = 1/N  separation of maxima
Resolving Power
N=100
Goes to zero at x=0.0628
= 2p/100
width = 1/N  separation of maxima