Question

If the lens is placed in water, then the refractive index with respect to water will be ________

(a) m=a/b

(b) m=b/a

(c) m*a=b

(d) m/b=a

This question was addressed to me in a national level competition.

This intriguing question originated from Lenses in division Optics of Engineering Physics II

Answer 1

Right choice is (a) m=a/b

Explanation: The refractive index of glass with respect to water, “m” is:

m=a/b

where, “m” is the refractive index of glass with respect to water, “a” is the refractive index of glass and “b” is the refractive index of water.

whereas, the refractive index of water with respect to glass, “n” (say) is:

n=b/a

=> n*a=b