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Physics Chp 15

Physics Chp 15. What happens when “light” hits a transparent material?. Some of it reflects and/or refracts Refraction is the bending of light due to a change in it’s speed in the new material. Index of refraction n = c/v 1 or greater.

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Physics Chp 15

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  1. Physics Chp 15

  2. What happens when “light” hits a transparent material?

  3. Some of it reflects and/or refracts • Refraction is the bending of light due to a change in it’s speed in the new material

  4. Index of refraction • n = c/v 1 or greater

  5. While θi=θr for reflection it isn’t always true for refraction, it depends in n • Snell’s Law • n1sinθ1 = n2sinθ2

  6. So why do objects under the water look closer to the surface and farther away from us than they really are?

  7. Why does “light” refract?

  8. Lenses use refraction to redirect light • Converging – brings the light towards the axis • Diverging – directs the light away from the axis

  9. Ray Diagrams • Converging • 1 – from tip parallel then towards f • 2 – from tip thru f then parallel • 3 – from tip thru center

  10. Ray Diagram • Diverging • 1- parallel then away from f • 2- towards far f then parallel • 3 – thru center

  11. Thin lens equation • Magnification equation

  12. Signs • f + converging • do + on the left of lens • di + on the right of lens • m + for upright

  13. Sketch a ray diagram for a converging lens with focal length of 1 m and the object 0.5 m left of the lens and 0.2 m tall. Then calculate the distance of the image as well as it’s height.

  14. Multiple Lenses image 1 = object 2

  15. Eye Type of lense? • Near point – closest object distance that still gives a clear image • Far point – farthest object distance that still gives a clear image

  16. Nearsightedness – far point issue, image in front of retina, use a diverging lens • Farsightedness – near point issue, image is behind the retina, use a converging lens

  17. Microscope • Telescope

  18. If n1 > n2 then there is an angle where θ2 = 90o • Sinθc = n2 / n1 • θc is the critical angle • If θ= θc then the “light” totally internally reflects

  19. Since each wavelength refracts differently prisms cause the rainbow from white light • Also rainbows in the sky are caused by water droplets dispersing the light back towards us.

  20. Lens Aberrations – not a single focal pt • Spherical aberrations – farther from the principal axis moves the focus • Chromatic aberrations – different wavelengths refracting differently

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