Announcements 3/25/11

1. Announcements 3/25/11 • Prayer • One lab due Saturday, two new labs start on Saturday. • We are nearing the homestretch for Optics… just two lectures after today. (After that, relativity!) • Exam 3 starts a week from tomorrow • Review session next Thurs or Friday. I sent survey link. I will schedule the room on Monday morning, so please select your favorite times before then.

2. Reading Quiz • Which of the following can generate a diffraction or interference pattern? • Light passing through a pinhole in a card • Light passing through an array of regularly spaced pinholes • Light clipped by the edge of a razor blade • Both A and B • All of the above

3. Review: Interference from slits • Quick writing: Using no equations, and in hopefully no more than two sentences, please explain how to solve slit problems.

4. A “wide” slit (book: “narrow” slits) • HW 34-3. How do we solve this? “a” = width of slit Result: New function: What is

5. The sinc function [sinc(x)]2 sinc(x) Image credit: http://scripts.mit.edu/~tsg/www/list.php?letter=Q

6. Single slit max/min • Under what conditions will you get a max? • Under what conditions will you get a min?

7. What you need to know • What sincx and sinc2x look like • The two formulas above (on notecard, unless you can quickly derive them) • How to do the integral (HW 34-3) • Conditions for max/min (on notecard, unless you can quickly derive them)

8. Thought Question • I shine light through two tiny slits spaced by d. Then I shine the same light through a single slit with width d. Which diffraction pattern has the broadest middle peak? • The two slit pattern • The single slit pattern • Both middle peaks are the same size. • Masspacity  Not the answer!!

9. λ = 5 a Image credit: Single slit diffraction pictures from Dr. Durfee

10. λ = a

11. λ = a/2

12. λ = a/3

13. λ = a/5

14. λ = a/10

15. Demo • Diffraction from a slit • Diffraction from a hair (Babinet’s principle, HW 34-2)

16. Reading Quiz • When you have two slits close to each other, each slit being “wide” (at least, not infinitely narrow), the intensity you get on the screen is: • A double-slit pattern • A “wide” single-slit pattern • A double-slit pattern PLUS a single-slit pattern • A double-slit pattern TIMES a single-slit pattern

17. Combination of patterns mins max max? • HW 34-4

18. x y 2-D patterns • Pattern from x-direction  Pattern from y-direction • Thought question: Which dimension of the rectangle was the narrowest? • X • Y zoomed in Example: rectangular aperture

19. Circular Aperture (more on this next time)

20. Rectangle & Circle, side-by-side

21. Array of Circles

22. Thought Question I shine light through a piece of foil which has two identical holes shaped like tiny llamas spaced apart by a distance d. What will the diffraction pattern look like? A : The same as two narrow slits separated by d. B : The same produced by a single slit of width d. C : The diffraction pattern of a single llama. D : The diffraction pattern of a single llama multiplied by the two-slit pattern. E : none of the above Credit: All llama slides are from Dr. Durfee