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Question
Define Snell's law of refraction. A ray of light is incident on a glass slab at an angle of incidence of 60°. If the angle of refraction be 32.7°, calculate the refractive index of glass. (Given : sin 60° = 0.866, and sin 32.7° = 0.540).
Solution
According to Snell's law, the ratio of sines of the angles of incidence and refraction is constant for a given pair of mediums.
We get:
sin i /sin r = n (constant)
This constant is called refractive index.
According to the question:
Angle of incidence, i = 60°
Angle of refraction, r = 32.7°
Refractive index, n = ?
Applying the above formula, we get:
sin i / sin r = n
or, n = sin 60°/ sin 32.7°
= 0.866/0.540 = 1.60
Thus, the refractive index of glass is 1.60.
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