Question

(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 × 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?

Answer 1

Explanation:

Answer

(a) Thespeed of light in a vacuum i.e., 3 × 108

m/s (approximately) is a universal

constant. It is not affected by the motion of the source, the observer, or both. Hence,

the given factor does not affect the speed of light in a vacuum.

(b) Out of the listed factors, the speed of light in a medium depends on the wavelength

of light in that medium.

Answer 2

★Given:

Refractive index of glass (μ) = 1.5

v = Velocity of light in a medium

Now, the Refractive index of medium is given as,

μ = Velocity of light in vacuum/ velocity of light in medium

1.5 =3.8m/sec÷v m/sec

v = 2×10⁸m/sec

Speed of light in glass is 2 × 10⁸ m/s.