Question

Find the refractive index of a medium having a velocity of 1.5 x 10^8.

(a) 0.5

(b) 5

(c) 0.2

(d) 2

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This is a very interesting question from Refractive Index and Numerical Aperture in division EM Wave Propagation of Electromagnetic Theory

Answer 1

Correct option is (d) 2

Easiest explanation: The refractive index is given by the ratio of the speed of light to the velocity in a particular medium. It is given by n = c/v. On substituting for v = 1.5 x 10^8 and c = 3 x 10^8, we get n = 3/1.5 = 2. The quantity has no unit.