A ray of light is incident at an angle of 30º on a glass prism of refractive index 1.5. Calculate the angle through which the ray is minimally deviated in the prism. (The medium surrounding the prism is air)
A
10.5o
B
19.5o
C
21.1o
D
38.9o
E
40.5o
Verified Correct Answer: C.
Physical Principles & Numerical Solution
n = \(\frac{sin i}{sin r}\)
sin r = \(\frac{30^o}{n}\)
sin r = \(\frac{0.5}{1.5}\)
sin r = 0.3333
r = sin\(^{-1}\)(0.333) = 19.5º
At minimum deviation, the ray passes symmetrically, so A = 2r
A = 2 x 19. 5 = 38.94
But minimum deviation = 2i - A
= 2 x (30º) - 38.94 = 21.06º
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Source: Myschool Past Questions Archive (Record #33400)