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The Art of Bending Light

The Art of Bending Light. It’s what we see…. Refraction. the bending of light when passing through a new (transparent) substance. Bending Light: Vocabulary. Incident Ray Angle of Incidence Normal Refracted Ray Angle of Refraction. Optical Density.

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The Art of Bending Light

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  1. The Art of Bending Light It’s what we see…

  2. Refraction • the bending of light when passing through a new (transparent) substance

  3. Bending Light: Vocabulary • Incident Ray • Angle of Incidence • Normal • Refracted Ray • Angle of Refraction

  4. Optical Density • How difficult it is for light to movethrough a substance . • High optical density  light travels through more slowly • Low optical density  light travels through more quickly

  5. Optical Density • How difficult it is for light to movethrough a substance . • High optical density  light travels through more slowly • Low optical density  light travels through more quickly

  6. Low to High Optical Density

  7. Low to much higher Optical Density

  8. High to lower Optical Density

  9. End Part I

  10. Quick Review • Notice when: • Light bends in • Light bends out

  11. Speeds of Light • Fast light • Slow light

  12. Optical Density • Ratio of old to new speed • n =optical density • Also known as index of refraction • c =speed of light • =speed of light in substance

  13. Speed of light • c = 3.00 x 108m/s • in a vacuum • In space,  = c • n = 1 in vacuum • Fastest in space. So… • n≥1 always!

  14. Index of Refractions • Table of indices of refraction for various substances

  15. Which substance has greatest n? Lowest?

  16. Trigonometry “Review” • SOHCAHTOA • sin  = IN OS AN

  17. Snell’s Law • Basic form • Compares angles d1 1 2 d2

  18. Working with Air • In a vacuum, • n = 1 • In air, • n = 1.0003 • Air is treated like a vacuum

  19. Snell’s Law from Air or Vacuum • In air, n = 1 • So, ignore n1 • Let’s solve for n2

  20. 1 2 3 How to choose the Equation ex) How fast is light in Water? • Speeds • Neither substance is air • One substance is air

  21. How fast is light in water? • n = 1.33 • c = 3.00 x 108m/s

  22. Example 2A ray of light passes from water to quartz (n = 1.54). The angle of incidence in the water is 35°. What is the angle of refraction? Given: Want:

  23. Refraction Activity! Go to pg. 64

  24. Example 3The photo below shows a smaller beaker inside a larger beaker. Wesson oil was poured into the larger beaker until it flowed about half way up the smaller beaker. Explain why the bottom of the beaker has disappeared. • n1n2 • Light does not bend between beakers

  25. Example 4The speed of light in a certain substance is 1.90 x 108m/s. If light passes from air into the substance at an angle of incidence of 54.0°, what will be the angle of refraction? Given: Want: Find n first!

  26. Example 4 Given: Want:

  27. Why? • Imagine rows of hikers • From dry land to swamp • Hikers in swamp slow down • Others stay fast • Angle Changed!

  28. OR… • Pierre de Fermat • Fermat’s Principle • Light always takes fastest path • So…

  29. Fastest Path • Is a straight line always the fastest?

  30. Fastest Path • Is a straight line always the fastest? • Dashed line is in slow substance for less time and in faster substance for more time. • Bent path is faster overall. d1<d2 d2 d1

  31. Snell’s Law Song • Singin’ n1 sine theta-sub-1, hey-hey-hey, Equals n2 sine theta-sub-2, hip hooray

  32. Atmospheric Refraction Effects Colors in the sky Air scatters light with small wavelengths Every color has its own wavelength (λ) Intensity of scattered light

  33. Lenses Focal point • Draw normals • Middle ray on normal • Middle ray does not refract • Light rays converge! • CONVERGING LENS

  34. Lenses Focal point • Normals again • Follow Rays Backwards! • Light rays diverge! • DIVERGING LENS

  35. Locating Images of Lenses • Remember Mirror Ray Patterns? • Lenses also have patterns! • Let’s break ‘em down!

  36. Converging Lens: Parallel Rays Holy cow! Through f!

  37. Converging Lens: From f ZOMG! Parallel!

  38. Converging Lens: Through Center Wowzers! Straight through!

  39. Diverging Lens: Parallel Rays Krikey! Away from f !

  40. Diverging Lens: Towards f Ka’Pow! Parallel!

  41. Diverging Lens: Through Center Mamma Mia! Straight Through!

  42. Find the Image Region Locations: • Same side as object • Between f and 2f • At 2f • Beyond 2f

  43. Time to Practice! Go to pg. 72

  44. Lens Movie

  45. Thin Lens Equations • Time for a new equation… • or

  46. Signs and Lenses

  47. Signs and Lenses

  48. Magnification Equation • Introducing…

  49. Multiple Lenses • Image of first lens is the object of the next!

  50. Galileo Inquisition Eppur Si Muove!

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