Ray Optics and Optical Instruments - Result Question 11
11. 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
Show Answer
Answer:
Correct Answer: 11. (b)
Solution:
- (b) By using $v=n \lambda$
Here, $n=2 \times 10^{14} Hz$
$\lambda=5000 \AA=5000 \times 10^{-10} m$
$v=2 \times 10^{14} \times 5000 \times 10^{-10}=10^{8} m / s$
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.
