Sample 1Medium
A ray diagram shows a glass prism of refracting angle 60° with a ray passing through it symmetrically, parallel to the base inside the prism. This is the position of minimum deviation, and the angle of minimum deviation is 30°. What is the refractive index of the glass?
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The answer is D.
n = sin[(A + D_m)/2] / sin(A/2) = sin 45° / sin 30° = 0.707/0.5 = √2 ≈ 1.41.
- A.
1.5 is a typical value for glass, but it does not follow from these angles.
- B.
1.73 is sin 60°/sin 30°, which uses A + D_m instead of (A + D_m)/2.
- C.
1.33 is the refractive index of water, not a result of this formula.
NCERT: Class 12 Physics, Chapter 9