Question

A light of wavelength $6000A^{\circ }$ and frequency $5\times {10}^{14}Hz$ in air enters a medium with refractive index 1.5. Inside the medium its frequency (in Hz) and wavelength (in $A^{\circ }$) respectively are

• A. $5\times {10}^{14}Hz,4000A^{\circ }$
• B. $9\times {10}^{14}Hz,6000A^{\circ }$
• C. $2.5\times {10}^{14}Hz,3000A^{\circ }$
• D. $9\times {10}^{14}Hz,6000A^{\circ }$

Answer 1

The correct option is A $5\times {10}^{14}Hz,4000A^{\circ }$

While travelling from one medium to other, frequency of light remains same.
${\lambda }_1=6000A^{\circ }$
We know,
$\frac{{\mu }_2}{{\mu }_1}=\frac{{\lambda }_1}{{\lambda }_2}$
or, $\frac{1.5}{1}=\frac{6000A^{\circ }}{{\lambda }_2}$
$\therefore {\lambda }_2=\frac{6000}{\left(\frac{3}{2}\right)}=4000A^{\circ }$

Why this question? Tip: Frequency of light is only dependent on the source producing it.