Q33 of 36 Page 1

Refractive index of water with respect to air is 1.33 and that of diamond is 2.42.

(i) In which medium does the light move faster, water or diamond?


(ii) What is the refractive index of diamond with respect to water?


Sol.


The refractive index of a substance is the ratio of the speed of light in a vacuum to the speed of light in the medium.


Since the refractive index of diamond is more, hence the speed of


light is lesser in a diamond.


Let the speed of light in water be vwand in diamond be vd.


Refractive index of diamond w.r.t water is, say n.


From the definition, we know



Dividing both numerator and denominator by speed of light [c], we


get


n = (vw/c) ÷ (vd/c)


Which is the inverse ratio of refractive index of water and diamond


n= 2.42/1.33 = 1.82 (approx.)


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