Question

A monochromatic beam of light of wavelength $6000A^{\circ }$ in vacuum enters a medium of refractive index $1.5$. In the medium its wavelength is _______ Its frequency is _________.

• A. $5000A;5\times {10}^{14}Hz$.
• B. $4000A;15\times {10}^{14}Hz$.
• C. $6000A;6\times {10}^{14}Hz$.
• D. $4000A;5\times {10}^{14}Hz$.

Answer 1

The correct option is D $4000A;5\times {10}^{14}Hz$.

$\mu =\frac{wavelengthinvaccum}{wavelengthinmedium}1.5=\frac{6000}{\lambda }$

$\lambda =4000$A

Now,

$c=\upsilon \lambda$

$\upsilon =\frac{c}{\lambda }=\frac{3\times {10}^8}{6000\times {10}^{-10}}=5\times {10}^{10}$Hz