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Today 1/29

Today 1/29. Lab Questions? Air wedges, soap films, coatings HW: 1/29 “Air Wedge” handout Due Friday 1/31 Thursday: Begin Ch 26 Refraction Peer guidance center (211 Wit) staffed: Mon - Thur, 1-4 Except Mon 2-3 and Tue 3-4 You are welcome to use room 211 anytime. Thin Films.

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Today 1/29

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  1. Today 1/29 • Lab Questions? • Air wedges, soap films, coatings • HW: 1/29 “Air Wedge” handout Due Friday 1/31 • Thursday: Begin Ch 26 Refraction • Peer guidance center (211 Wit) staffed:Mon - Thur, 1-4 Except Mon 2-3 and Tue 3-4You are welcome to use room 211 anytime.

  2. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  3. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  4. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  5. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  6. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  7. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  8. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  9. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  10. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  11. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  12. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  13. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  14. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  15. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  16. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  17. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  18. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  19. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  20. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  21. Thin Films No phase shift means that a trough bounces off a boundary as a trough and a crest bounces off a boundary as a crest. Now invert the reflected wave (phase shift). This is like light bouncing off of a higher n material. Trough in Trough out Incoming wave Reflected wave Crest in Crest out

  22. Thin Films Phase shift means that a trough bounces off a boundary as a crest and a crest bounces off a boundary as a trough. Now invert the reflected wave (phase shift). This is like light bouncing off of a higher n material. Trough in Crest out Incoming wave Reflected wave Crest in Trough out

  23. Thin Films Phase shift means that a trough bounces off a boundary as a crest and a crest bounces off a boundary as a trough. Trough in Crest out Incoming wave Reflected wave Crest in Trough out

  24. Thin Films Phase shift means that a trough bounces off a boundary as a crest and a crest bounces off a boundary as a trough. Trough in Crest out Incoming wave Reflected wave Crest in Trough out

  25. Thin Films Phase shift means that a trough bounces off a boundary as a crest and a crest bounces off a boundary as a trough. Trough in Crest out Incoming wave Reflected wave Crest in Trough out

  26. Thin Films Phase shift means that a trough bounces off a boundary as a crest and a crest bounces off a boundary as a trough. Trough in Crest out Incoming wave Reflected wave Crest in Trough out

  27. Thin Films Phase shift means that a trough bounces off a boundary as a crest and a crest bounces off a boundary as a trough. Trough in Crest out Incoming wave Reflected wave Crest in Trough out

  28. Thin Films Phase shift means that a trough bounces off a boundary as a crest and a crest bounces off a boundary as a trough. Trough in Crest out Incoming wave Reflected wave Crest in Trough out

  29. Thin Films Phase shift means that a trough bounces off a boundary as a crest and a crest bounces off a boundary as a trough. Trough in Crest out Incoming wave Reflected wave Crest in Trough out

  30. Thin Films Phase shift means that a trough bounces off a boundary as a crest and a crest bounces off a boundary as a trough. Trough in Crest out Incoming wave Reflected wave Crest in Trough out

  31. Thin Films Phase shift means that a trough bounces off a boundary as a crest and a crest bounces off a boundary as a trough. Trough in Crest out Incoming wave Reflected wave Crest in Trough out

  32. Thin Films Phase shift means that a trough bounces off a boundary as a crest and a crest bounces off a boundary as a trough. Trough in Crest out Incoming wave Reflected wave Crest in Trough out

  33. Thin Films Phase shift means that a trough bounces off a boundary as a crest and a crest bounces off a boundary as a trough. Trough in Crest out Incoming wave Reflected wave Crest in Trough out

  34. Thin Films Phase shift means that a trough bounces off a boundary as a crest and a crest bounces off a boundary as a trough. Trough in Crest out Incoming wave Reflected wave Crest in Trough out

  35. Thin Films Phase shift means that a trough bounces off a boundary as a crest and a crest bounces off a boundary as a trough. Trough in Crest out Incoming wave Reflected wave Crest in Trough out

  36. Thin Films Phase shift means that a trough bounces off a boundary as a crest and a crest bounces off a boundary as a trough. Trough in Crest out Incoming wave Reflected wave Crest in Trough out

  37. Thin Films Phase shift means that a trough bounces off a boundary as a crest and a crest bounces off a boundary as a trough. Trough in Crest out Incoming wave Reflected wave Crest in Trough out

  38. Thin Films Phase shift means that a trough bounces off a boundary as a crest and a crest bounces off a boundary as a trough. Trough in Crest out Incoming wave Reflected wave Crest in Trough out

  39. Thin Films Phase shift means that a trough bounces off a boundary as a crest and a crest bounces off a boundary as a trough. Trough in Crest out Incoming wave Reflected wave Crest in Trough out

  40. Thin Films Phase shift means that a trough bounces off a boundary as a crest and a crest bounces off a boundary as a trough. Trough in Crest out Incoming wave Reflected wave Crest in Trough out

  41. Antireflection coatings Setting up destructive interference for reflected light means that it all (mostly) is transmitted. Can’t do it for all wavelengths at once so choose green, in the middle of the visible spectrum. When n coating < n glass... ...both reflected rays phase shifted so 2t = (m + 1/2)  coating gives destructive interference in the reflection. Coating Lens …only one reflected ray is phase shifted so 2t = (m) coating gives destructive interference in the reflection. When n coating > n glass...

  42. Eyeball Thin Films The wavelength is different in the film. Wavelength ()Film thickness (PLD)Index of refraction (n)Phase shifts film = vacuum /nfilm

  43. Thin Film Problems • Draw picture • Consider reflected wave phase shifts • none, one, or both can be shifted • Find  in the film • Chose m or (m + 1/2) (use in the film) • Constructive or destructive? • Phase shifts? • PLD = 2t for thin films

  44. Example: 665 nm light shines on a soap film nearly perpendicularly. The soap film has n = 1.33. What is the minimum thickness of the film if this wavelength is strongly reflected? For air n = 1. One is phase shifted (front surface), the back surface reflection is not phase shifted.  film = /n film = 665 nm /1.33 = 500 nm Want constructive but one is phase shifted so... we use (m + 1/2) film 2t = (m + 1/2) film minimum t when m = 0 2tmin = (1/2) film tmin = (1/4) film = 125 nm

  45. 1500 nm500 nm300 nm214 nm 2000 nm665 nm399 nm285 nm Visible light Example: See example 11 Ch 27 Light shines on a soap film nearly perpendicularly. The film is 375 nm thick and has n = 1.33. List the first four wavelengths of light for which constructive interference causes the film to look bright in reflected light. 2t = ? (m + 1/2) film since only one is phase shifted  film  air = nfilm film

  46. Thin Films, Wedges Vertical soap film is thicker at the bottom. Pair of thick glass plates with a thin air wedge in between. The air is the thin film. Both will produce light and dark fringes because the thickness varies.

  47. t = 3/4 film t = 5/4 film t = 7/4 film t = 9/4 film Thin Films, Wedges Soap film in reflected light. Thin at the top. 2t < 1/2 film t < 1/4 film!!! 2t = 1/2 film t = 1/4 film 2t = 3/2 film 2t = 5/2 film 2t = 7/2 film 2t = 9/2 film 2t = (m + 1/2)  film for constructive since only one ray is phase shifted.

  48. Thin Films, Wedges Air wedge in reflected light. Thin at the left. One is phase shifted and one is not so for constructive interference.... 2t = (m + 1/2)  airIt’s an “air” film Top view Where the glass touches, it will be dark. Why?

  49. Transmitted Thin Films, Wedges What about the transmitted light? No light reflected means all transmitted! Reflected This is easy to observe This is hard to observe

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