STANDARD Physics Prisms and Refraction MCQ Question
The refractive index of the material of a prism is √2 and the angle of the prism is 30°. One of the two refracting surface of the prism is made a mirror inwards, by silver coating. A beam of monochromatic light entering the prism from the other face will retrace its path (after reflection from the silvered surface) if its angle of incidence on the prism is?
30°
60°
Zero
45°
Correct Answer
Detailed Explanation
Using Snell’s law, 1 × sin i = μ × sin r. 1 × sin i = √2 × sin 30 = √2/2. Therefore, sin i = √2/2, which gives i = 45°.
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