Question

Suppose a light wave has wavelength $\left(\lambda \right)$, frequency $\left(\nu \right)$ and speed $\left(c\right)$ in the air $({\mu }_a=1)$ . It passes through a medium with refractive index $\left(\mu \right)$. The modified wavelength, frequency and speed would be-

• A. $\frac{\lambda }{\mu };\frac{\nu }{\mu };\frac{c}{\mu }$
• B. $\frac{\lambda }{\mu };\nu ;\frac{c}{\mu }$
• C. $\lambda ;\nu ;\frac{c}{\mu }$
• D. $\frac{\lambda }{\mu };\frac{\nu }{\mu };c$

Answer 1

The correct option is B $\frac{\lambda }{\mu };\nu ;\frac{c}{\mu }$

When light is refracted into a medium, its wavelength changes, but frequency remains unchanged.

Hence, $\lambda {}^{\prime }=\frac{\lambda }{\mu }$ and $\nu {}^{\prime }=\nu$

And we know, $c=\lambda \nu$

$c{}^{\prime }=\lambda {}^{\prime }\nu {}^{\prime }=\frac{\lambda }{\mu }\nu =\frac{c}{\mu }$

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Hence, $\left(\text{B}\right)$ is the correct answer.