The angle of refraction (r) of a ray of white light from air through a triangular glass prism of refractive index 1.5 is 29.0°. Calculate the angle…
Source: JAMB · 2024
The angle of refraction (r) of a ray of white light from air through a triangular glass prism of refractive index 1.5 is 29.0°. Calculate the angle through which the ray it least deviated.
Explanation
The ray is least deviated at minimum deviation. Here the ray passes symmetrically through the prism, so the angle of refraction r is half the prism angle A.
A = 2r = 2 × 29.0° = 58.0°.
Find the angle of incidence i from Snell’s law: sin i = n × sin r = 1.5 × sin 29.0° = 1.5 × 0.4848 = 0.7272. So i ≈ 46.7°.
Minimum deviation D = 2i − A = 2(46.7°) − 58.0° ≈ 35.3°.
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