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Chapter 17

Chapter 17. Reflection & Refraction. Reflection. When light rays bounce back off of a medium boundary. Refraction. The bending of light rays when passing from one medium to another. Ray. A straight line path representing the direction of a light wave. Regular Reflection.

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Chapter 17

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  1. Chapter 17 Reflection & Refraction

  2. Reflection • When light rays bounce back off of a medium boundary

  3. Refraction • The bending of light rays when passing from one medium to another

  4. Ray • A straight line path representing the direction of a light wave

  5. Regular Reflection • Reflection off of a smooth surface which results in reflected wave that are parallel

  6. Regular Reflection • Produce good images • Mirrors give regular reflections

  7. Diffuse Reflection • Reflection off of a rough surface which results in reflected waves that are not parallel

  8. Diffuse Reflection • Because light waves are scattered all over the place, no image can be seen

  9. Law of Reflection • The angle of reflection equals the angle of incident

  10. Law of Reflection b = a a Normal  b

  11. Optical Density • How fast light passes through a substance as compared to the speed of light in a vacuum.

  12. Optical Density • As optical density increases, the speed in which light passes decreases

  13. Index of Refraction (n) • Ratio of the speed of light in a vacuum to the speed of light in a material

  14. Indices of Refraction • Vacuum: n = 1.00 • Air: n = 1.0003 • Water: n = 1.33 • Ethanol: n = 1.36

  15. Indices of Refraction • Crown glass: n = 1.52 • Quartz: n = 1.54 • Flint glass: n = 1.61 • Diamond: n = 2.42

  16. Speed of Light in Other Substances c vsub nsub =

  17. Speed of Light in Other Substances c nsub vsub =

  18. Solve for the speed of light in each of the following:water (n = 1.33)crown glass (n = 1.52)diamond (n = 2.42)

  19. Solve for the speed of light in a substance with an optical density of 1.50:

  20. Snell’s Law • The ratio of the sine of the angle of incidence over the sine of the angle of refraction is constant for any substance

  21. Snell’s Law sin ai sin ar n =

  22. Snell’s Law ni sin ai = nr sin ar

  23. Snell’s Law ar ai n2 = water n1 = air

  24. Draw a model with a light ray passing from one medium to another more optically dense medium. Include reflection & refraction

  25. A light ray from air (nair = 1.00) & strikes glass (nglass = 1.52) with an incident angle of 30.0o. Calculate the angle of refraction:

  26. A light ray from air (nair = 1.00) strikes glass (nglass = 1.61) with an incident angle of 36.9o. Calculate the angle of refraction:

  27. A light ray from air (nair = 1.00) & strikes diamond (ndiamd = 2.42) with an incident angle of 45.0o. Calculate the angle of refraction:

  28. A light ray incident from air (nair = 1.00) at 45.0o passes into an unknown substance at 30.0o. Calculate its index of refraction:

  29. Total Internal Reflection • When light passes from a more optically dense substance to a less optically dense one, the angle of refraction > the angle of incident

  30. b a

  31. Total Internal Reflection (TIR) • When the angle of refraction  90o, total internal reflection occurs.

  32. Calculate the angles where TIR occurs when light passes from the following to air:water (n = 1.33)crown glass (n = 1.52)diamond (n = 2.42)

  33. Applications & Effects • Prisms • Fiber Optics • Mirages • Red Sunsets • Rainbows

  34. Prisms • When light pass through a prism the various wavelengths of light are dispersed or separated into a spectrum

  35. Prisms

  36. Fiber Optics • A light wave can pass through a thin glass thread surrounded by a reflective substance. Even if the glass thread is bent, the wave passes through as it reflects off the sides.

  37. Mirages • Light refracted from a far away source looks closer

  38. Mirages

  39. Sunsets & Rises • Sunlight is refracted as it strikes the atmosphere at great angles bending light towards Earth

  40. Sunsets • Because different wavelengths are refracted differently, colors change

  41. Sunsets

  42. Rainbows • Sunlight is refracted & reflected by rain droplets dispersing the light into a spectrum

  43. Rainbows

  44. Rainbows Rainbows fall from 40 – 42o from incident

  45. Rainbows Rainbows fall from 40 – 42o from incident

  46. A light ray from water (nw = 1.33) & strikes diamond (ndiamd = 2.42) with an incident angle of 53.0o. Calculate the angle of refraction:

  47. Answer the questions at the end of Chapter 16

  48. Answer the questions at the end of Chapter 17

  49. A light ray from water (nw = 1.33) & strikes glass (nglass = 1.51) with an incident angle of 53.0o. Calculate the angle of refraction:

  50. Calculate the angle of total internal reflection of pukon with n = 3.00

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