Download Refraction - E. R. Greenman

REFRACTION
Physics Chapter 18b
Refraction
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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
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Property of medium that determines speed of light in that medium
Snell's Law
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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
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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
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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
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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
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(1.0003)(.5) = 1.52sinΘ
0.50015/1.52 = sinΘ
0.329046053 = sinΘ
Θ = 19.210885 = 19.2o