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internal reflection
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02/03/2015 Total Internal Reflection
http://hyperphysics.phyastr.gsu.edu/hbase/phyopt/totint.html 1/2
Total Internal ReflectionWhen light is incident upon a medium of lesser index of refraction, the ray isbent away from the normal, so the exit angle is greater than the incident angle.Such reflection is commonly called "internal reflection". The exit angle willthen approach 90° for some critical incident angle θc , and for incident anglesgreater than the critical angle there will be total internal reflection.
The critical angle can be calculated from Snell's law by setting the refractionangle equal to 90°. Total internal reflection is important in fiber optics and isemployed in polarizing prisms.
For any angle of incidence less than the critical angle, part of the incident lightwill be transmitted and part will be reflected. The normal incidence reflectioncoefficient can be calculated from the indices of refraction. For nonnormalincidence, the transmission and reflection coefficients can be calculated fromthe Fresnel equations.
For total internal reflection of light from a medium of index of refraction
Index
Reflectionconcepts
02/03/2015 Total Internal Reflection
http://hyperphysics.phyastr.gsu.edu/hbase/phyopt/totint.html 2/2
n1 = ni = ,
the light must be incident on a medium of lesser index. If the new medium has
n2 = nt =
then the critical angle for internal reflection is θc = degrees.
If values for n1 and n2 are entered above, the critical angle θc for total internalreflection will be calculated. (For example, θc = 48.6° for water and air.) Butthe angle for total internal reflection can be measured and used to determine theindex of refraction of a medium. If a new value of θc is entered above, then thecorresponding value of n1 will be calculated.
Plot of internal reflection coefficients
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