## Lecture 12: Diffraction and Diffraction Gratings

February 27, 2018

• Read: 32.3, 32.5, 32.6; Supplementary Reading Ch 1.5, 1.6, 1.7, 1.8
• Study: Fig 32.8, 32.24, 32.26; Supp. Exs. 1-6, 1-7, 1-8
• Skim: 32.4
• Ignore: Eq 32.10

### Objectives

• (Continuing objective) Describe applications of the concepts of induction, waves, and light to everyday real life'' situations.
• Use the method of phasors to locate maxima and minima in a two-slit interference problem, multi-slit interference pattern, or for diffraction gratings.
• Explain how diffraction gratings can be used to separate colors.
• Using phasors, determine the phase difference corresponding to successive minima in a single slit diffraction pattern. From this, find the angles and screen locations of minima and determine the width of the bright'' central maximum.
• Describe diffraction, and explain how diffraction limits resolution. Use Rayleigh's criterion to solve resolution problems.

### Homework

• Wednesday's Assigned Problems: A45, A46; CH 32: 19, 27, 31, 33, 41; Supp CH 1: 7, 9
• Monday's Hand-In Problems: A47, A105; CH 32: 18, 42; Supp CH 1: 8; Supp CH 2: 2, 8, 11, 12, 15

### Videos of example problems

To see the problem statement, click on the link below. To play the video example, click on the underlined words "Video Demonstration" near the top of the page with the problem statement.
• Example 1: Resolution limits. Note: This problem uses Rayleigh's criterion for a circular aperture, which includes a factor of 1.22. Since we use $\theta_{min} \approx \frac{\lambda}{D}$, you can include the factor of 1.22 or not (this is an approximation!).