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REFRACTION Physics Chapter 18b Refraction Bending rays of light as it passes from one medium to another Caused by change in speed of wave Amount of refraction depends on angle of incidence and properties of the two media Optical density Property of medium that determines speed of light in that medium Snell's Law Each medium has a characteristic change in the speed of the wave This characteristic is called the index of refraction Amount of bending depends on the index of refraction For a wave travelling from a vacuum into another medium: n = sin i sin r • TABLE OF INDEX OF REFRACTION VALUES • (For Sodium yellow light): • Material • • • • • • • • • INDEX OF REFRACTION: n=c/v Water 1.33 Fused quartz 1.46 Crown glass 1.52 Lucite or Plexiglass 1.51 Diamond 2.42 Ethyl Alcohol 1.36 Air (at STP) 1.0003 Light flint 1.58 Sodium chloride 1.53 Snell's Law for Any Two Media Index of refraction of first medium times the sine of the angle of incidence equals the index of refraction of the second medium times the sine of the angle of refraction Both angles measured from normal Example A light beam in air hits a sheet of crown glass at an angle of 30o. At what angle is the beam refracted? What we know: incident angle 30o incident n: 1.0003 refracting n: 1.52 Equation: n1sinΘ1 = n2sinΘ2 Put values in: (1.0003)sin30 = (1.52)sinΘ Example Continued (1.0003)(.5) = 1.52sinΘ 0.50015/1.52 = sinΘ 0.329046053 = sinΘ Θ = 19.210885 = 19.2o