Unit: wave phenomena
Year: 1988 Question#: 39
Question: In the diagram below, a monochromatic light ray is passing from medium A into medium B. The angle of incidence
is varied by moving the light source S
. When angle 
becomes the critical angle, the angle of refraction will be
(1 ) 0 degrees
(2 )
(3 ) greater than
,
but less than 90 degrees(4 ) 90 degrees
What is this question really asking?
Explanation by: Esy C
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Answer 1
0 degrees
INCORRECT
This doesn't make sense; the angle wouldn't be along the normal line. Consult the definition of a critical angle. return to top
Answer 2
INCORRECT
This doesn't make sense; the ray does change course as it enters a faster medium. return to top
Answer 3
greater than
, but less than 90 degreesINCORRECT
This would be true if the angle were any angle but the critical angle. return to top
Answer 4
90 degrees
CORRECT
The critical angle (by definition) is the angle of incidence at which the angle of refraction equals 90°. return to top
What's this question really asking?
What is the angle of refraction for the critical angle? return to top
