1. PHENOMENA OF LIGHT Chapters 27, 29, & 31

2. Easy to get mixed up… Polarization (Light)Ch 27 Reflection (Water & Light)Ch 29 Refraction (Light)Ch 29 Dispersion (Rainbows)Ch 29 Total Internal Reflection (TIR)Ch 29 Diffraction (Water & Light)Ch 31 Interference (Water & Light)Ch 31 Thin Film Interference (Oil in the Gutter)Ch 31 LASERS (Monochrome & Coherent)Ch 31

3. Polarization Intensity varies as polarizer is rotated Courtesy Siltec Ltd.

4. Polarization Courtesy of 3M Corporation In linear Polarization light vibrations become confined to a single linear plane

5. Propagation of a Linearly Polarized Electromagnetic Wave Animation Courtesy Siltec Ltd. http://www.infoline.ru/g23/5495/Physics/English/feedback.htm

6. Reflection Light bounces off objects Consider “rays” – light moving in straight line Law of reflection: angle of incidence = angle of reflection

7. Law of Reflection  i =  r I - incident ray R - reflected ray N – normal Theta-I is angle of incidence Theta –R is angle of reflection

8. How Curved Mirror Forms Real Images

9. Refraction: How Much Does It Bend Angle of incidence  i Angle of refraction  r Snell’s Law: n i sin  i = n r sin  r

10. Helpful Analogy: The Band of Sand What happens when a car drives into the sand? highway sand Which way does the car turn?

11. Toward and Away from Normal When light enters a more dense (greater n) medium, it bends toward the normal When light enters a less dense (smaller n) medium, it bends away from the normal

12. Index of Refraction Ratio of speed of light in vacuum to speed of light in material n = c/v = 3.0 x 10 8 m/s /v n always greater than one

13. Dispersion Spreading of white light into spectrum of wavelengths

14. Why Dispersion Occurs Index of refraction, n, depends on wavelength Typically n decreases as  increases Exit angle from prism depends on White light

15. Forming a Rainbow Way Complex Applet … Java Applet

18. Total Internal Reflection Fiber Optics – NOT just Light but INFORMATION Diamonds – very bright!!

19. Diffraction Bending of Light around an obstacle, a corner or a slit

20. Predict This What happens when a beam of light goes through two tiny slits? What pattern do you expect on the screen beyond?

21. Double Slit Interference Applet What if light from two slits interferes? http://www.ece.gatech.edu/research/ccss/educa tion/Java/1998.Winter/Projects/pierce- woods/project/bin/projApp.htm Experiment performed by Young in 1801 Convincing evidence for wave nature of light Another Double Slit AppletAnother Double Slit Applet (Not at this time)

22. Varying the Slit Separation Courtesy of Siltec Ltd. http://www.infoline.ru/g23/5495/Physics/English/feedback.htm

23. Single Slit Interference Also called diffraction Fringes are larger Size of fringes decreases out from center of pattern Derivation, not Single and duel with sound and a listener http://phet.colorado.edu/new/simulations/sims.php?sim=Sound

24. More On Single Slit Interference Pattern dominated by central maximum Called central diffraction maximum Width measured from minimum to minimum Twice as wide as other fringes Much brighter than other fringes http://phet.colorado.edu/new/simulations/sims.php?sim= Wave_Interference

25. Single Slit Diffraction- Varying the Slit Width Fringes get bigger as slit gets smaller

26. Diffraction Gratings Diffraction Grating has thousands of lines per cm cut into glass plate Light from each slit interferes with light from all other slits Analysis like Double Slit Sin  = m /d principal maxima (bright) Lines very close so maxima occur at large angles   is maximum possible so only a few maxima (“orders”)exist

27. Spectrum Produced by Grating

28. Thin Film Interference Let film thickness = t Assume no net phase change on reflection 2t = m  m  Condition for bright 2t = (m+1/2) Condition for dark For one hard reflection 2t =m  becomes condition for dark

29. Examples of Thin Film Interference Oil on Water Soap Bubbles Anti-reflective coating on lens

30. LASERS Big and Small