Question

For the same angle of incidence in media A,B and C, the angles of refraction are 200, 300 and 400 respectively. In which medium will the velocity of light be maximum? Give reason in support of your answer.

Answer 1

The speed of light will be maximum in medium C

If the velocity of light in the medium is v , refractive index is μ and c be the velocity of light in free space then we know that,

μ = c/v

=> v = c/μ

Now we know that refractive index is given by,

μ = sin i / sin r

Hence,

v = c sin r / sin i

since c and sin i are equal for all the mediums, hence

v ∝ sin r

Hence the greater the value of angle of refraction => the greater the value of speed of light in that medium

Hence the speed of light will be maximum in medium C as it has the highest value of angle of refraction(400)

Answer 2

From Snell’s law

n = sin i /sin r = c/v

Since c and sin i are constant therefore sin r is directly proportional to v

Therefore velocity of light is maximum in medium C.

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