Announcements 11/16/11 Prayer Labs 8, 9 due Saturday. Lab 10 due Tuesday. We are nearing the homestretch for Optics… just two lectures after today. (After that, relativity!) We do have class Tuesday of next week Exam 3 starts Monday after Thanksgiving break Vote for review session, Mon/Tues/Wed next week Pearls Before Swine

Reading Quiz A single slit diffraction pattern is characterized by: a. a.A narrow central maximum, with other maxima and minima on each side b. b.A narrow central minimum, with other maxima and minima on each side c. c.A wide central maximum, with other maxima and minima on each side d. d.A wide central minimum, with other maxima and minima on each side

Review: Interference from slits Quick writing: Using no equations, and in hopefully no more than two sentences, please explain the basic idea(s) behind solving slit problems.

A “wide” slit (book: “narrow” slit) HW How do we solve this? Result: New function: What is “a” = width of slit

The sinc function sinc(x) [sinc(x)] 2 Image credit: www/list.php?letter=Q

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

What you need to know Given on exam Not given on exam two narrow slits: one wide slit:

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? a. a.The two slit pattern b. b.The single slit pattern c. c.Both middle peaks are the same size.

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

λ = a

λ = a/2

λ = a/3

λ = a/5

λ = a/10

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

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. a.A double-slit pattern b. b.A “wide” single-slit pattern c. c.A double-slit pattern PLUS a single-slit pattern d. d.A double-slit pattern TIMES a single-slit pattern

Combination of patterns HW 34-4 max mins max?

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

Circular Aperture (more on this next time)

Rectangle & Circle, side-by-side

Array of Circles

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

Important: No llamas were harmed in the making of these images