Ray Optics and Optical Instruments - Result Question 19
19. An electromagnetic radiation of frequency $n$, wavelength $\lambda$, travelling with velocity $v$ in air enters in a glass slab of refractive index $(\mu)$. The frequency, wavelength and velocity of light in the glass slab will be respectively
[1997]
(a) $n, \frac{\lambda}{\mu}$ and $\frac{v}{\mu}$
(b) $n, 2 \lambda$ and $\frac{v}{\mu}$
(c) $\frac{n}{\mu}, \frac{\lambda}{\mu}$ and $\frac{v}{\mu}$
(d) $\frac{2 \pi}{\mu}, \frac{\lambda}{\mu}$ and $v$
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Answer:
Correct Answer: 19. (a)
Solution:
- (a) For e.m. wave entering from air to glass $slab(\mu)$, frequency remains $n$,
wavelength, $\lambda^{\prime}=\frac{\lambda}{\mu}$ and velocity, $v^{\prime}=\frac{v}{\mu}$
When electromagnetic wave enters in other medium, frequency remains unchanged while wavelength and velocity become $\frac{1}{\mu}$ times.
