Ray Optics And Optical Instruments Ques 7
7. The frequency of a light wave in a material is $2 \times 10^{14} $ $Hz$ and wavelength is $5000 $ $\AA$. The refractive index of material will be
[2007]
(a) $1.50$
(b) $3.00$
(c) $1.33$
(d) $1.40$
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Answer:
Correct Answer: 7.(b)
Solution:
- (b) By using $v=f \lambda$
Here, $n=2 \times 10^{14}$ $ \text{Hz} $
$\lambda=5000 $ $\AA=5000 \times 10^{-10}$ $ m$
$v=2 \times 10^{14} \times 5000 \times 10^{-10}=10^{8} $ $m / s$
Refractive index of the material.
$\mu=c / v=\frac{3 \times 10^{8}}{10^{8}}=3$
In case of refraction of light frequency (and hence colour) and phase do not change while wavelength and velocity will change.
BETA
