Question

A light wave has a frequency of $4\times {10}^{14}Hz$ and wavelength of $5\times {10}^{-7}m.$ The refractive index of the medium in which it is travelling is :

• A. 1.2
• B. 2.4
• C. 1.5
• D. 1.75

Answer 1

The correct option is C 1.5

Velocity of light in the medium,
$C_m=\nu \lambda$
$=(4\times {10}^{14})\times (5\times {10}^{-7})$
$=2\times {10}^{8}m/sec.$
Velocity of light in vaccum, $C_v=3\times {10}^{8}m/sec$
$\therefore \mu =\frac{C_v}{C_m}=\frac{3\times {10}^8}{2\times {10}^8}=1.5$