Class 12 Physics
CBSE and UP Board
Wave Optics
Chapter-10 Exercise 10.3
NCERT Solutions for Class 12 Physics Chapter 10 Question-3
(a) The refractive index of glass is 1.5. What is the speed of light in glass? Speed of light in vacuum is 3.0 x 10⁸ m s⁻¹) (b) Is the speed of light in glass independent of the colour of light? If not, which of the two colours red and violet travels slower in a glass prism?
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Ans (a).
Refractive index of glass, μ = 1.5
Speed of light, c = 3 x 108 m/s
Speed of light in glass is given by the relation,
v =c/μ
= (3×108)/1.5 = 2 x 108 m/s.
Hence, the speed of light in glass is 2 x 108 m/s.
Ans (b).
The speed of light in glass is not independent of the colour of light.
The refractive index of a violet component of white light is greater than the refractive index of a red component. Hence, the speed of violet light is less than the speed of red light in glass. Hence, violet light travels slower than red light in a glass prism.