1. Lecture 28, Wednesday April 15 Diffraction Grating Thin Film Interference Single Slit Diffraction

2. Problems due Today 17: 13, 17, 19, WB 25: 1-18 13: diffraction grating 17: ditto 19: skip b WB 17: 1-9 pictures of interference 25: 19, 22, 28, 29, 31

3. Two slit interference Young demonstrated light behaved as a wave. Bright fringes occurred at angles For small angles

4. QUIZ # 9 Two narrow slits 0.04 mm apart are illuminated by light from a HeNe laser (λ = 633 nm). A. What is the angle of the first (m = 1) bright fringe? B. What is the angle of the thirtieth bright fringe? Slide 17-11

5. Index of Refraction—cf. Lab last week Index of refraction

6. The Diffraction Grating Slide 17-12

7. The Intensity Pattern Due to a Diffraction Grating Slide 17-14

8. The Fringes Become Very Narrow as the Number of Slits is Increased Slide 17-15

9. A Diffraction Grating Splits Light into the Wavelengths That Make It Up Slide 17-16

10. All waves spread out after passing through a small enough gap in a barrier. This phenomenon is known as 1.Antireflection 2.double-slit interference 3.Refraction 4.diffraction

11. Problems due Friday 17: 1, 2, 4, 7, 9, 10, 12 2: speed in glass 4: wavelength in glass 7: two slit interference 9: ditto, given d and y 5 – y 1, find λ 10: two slits given fringe spacing, λ 12: Δr

12. Problems 25: 19 E = 10 V/m in an electromagnetic wave. What is B? 22: – What is λ, f, and electric field amplitude? 28: I = 10 W/m 2 for a linearly polarized wave. Intensity through polarizer with b) θ = 30 0 ?

13. More Problems 29: 25% passes polarizer. Angle of polarizer with respect to electric field? 31: Unpolarized light with I = 350 W/m 2 – What is I after two polarizers with second axis 35 0 to axis of first?

14. Problems 17 CQ1: frequency in water, glass CQ3: change in λ n, does it change apparent color? MC17: what changes when light enters glass? 1: travel time through piece of glass

15. Thin-Film Interference Slide 17-17

16. Phase Changes Due to Reflection Slide 17-18

17. Analyzing Thin-Film Interference Slide 17-19

18. Single-Slit Diffraction Light passing through a narrow slit spreads out beyond the slit. Slide 17-23

19. Analyzing Single-Slit Diffraction Slide 17-24

20. Single-Slit Diffraction: Positions and Intensities Slide 17-25