Unit: waves
Year: 1997 Question#: 44
Question: The absolute index of refration for a substance is 2.0 for light having a wavelength of 5.9 * 10-7 meter. In this substance, what is the critical angle for light incident on a boundary with air?
(1 ) 30 degrees
(2 ) 45 degrees
(3 ) 60 degrees
(4 ) 90 degrees
What is this question really asking?
Explanation by: Ajemo H
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Answer 1
30 degrees
CORRECT
The equation for the critical angle is sin
=1/n. where n= absolute index of refraction, and 
equals the degrees of the critical angle. If you plug 2.0 for the absolute index
of refraction, then you just find the sin of what equals 1/2.return to top
Answer 2
45 degrees
INCORRECT
The equation for the critical angle is sin
=1/n. where n= absolute index of refraction, and theta equals the degrees of the critical
angle.
return to top Answer 3
60 degrees
INCORRECT
The equation for the critical angle is sin
=1/n. where n= absolute index of refraction, and 
equals the degrees of the critical angle.
return to top Answer 4
90 degrees
INCORRECT
The equation for the critical angle is sin
=1/n. where n= absolute index of refraction, and 
equals the degrees of the critical angle.
return to top What's this question really asking?
This question is asking if you know how to use the formula for the critical angle. It also asks if you know some basic trigometric functions. return to top
