Q91 / 160 · JIPMER 2009 · Physics
The frequency of a light wave in a material is $2 \times 10^{14} \mathrm{~Hz}$ and wavelength is $5000 Å$. The refractive index of material will be
- A1.40
- B1.50
- Correct answerC3.00
- D1.33
Solution
Velocity of light waves in material is
$v=\mathrm{v} \lambda\ldots(i)$
Refractive index of material is
$\mu=\frac{c}{v}\ldots(ii)$
where $c$ is speed of light in vacuum or air.
or
$\mu=\frac{c}{v \lambda}\ldots(iii)$
Given, $\quad v=2 \times 10^{14} \mathrm{~Hz}$,
$\begin{aligned}
\lambda & =5000 Å=5000 \times 10^{-10} \mathrm{~m}, \\
c & =3 \times 10^8 \mathrm{~m} / \mathrm{s}
\end{aligned}$
Hence, from Eq. (iii), we get
$\mu=\frac{3 \times 10^8}{2 \times 10^{14} \times 5000 \times 10^{-10}}=3.00$
Hence, the correct answer is option: 'C'.