Question

A light wave has a wavelength of $10\stackrel{\circ }{A}$. Find its frequency if speed of light is 300000 km/second.

• A. $300000Hz$
• B. $30000Hz$
• C. $3\times {10}^{17}Hz$
• D. $3\times {10}^{6}Hz$

Answer 1

The correct option is C $3\times {10}^{17}Hz$

$\lambda =10\stackrel{\circ }{A}=10\times {10}^{-10}m$
$v=300000km/s=3\times {10}^{8}m/s$
We know that $V=f\lambda \Rightarrow f=\frac{V}{\lambda }$
$=\frac{3\times {10}^8}{10\times {10}^{-10}}=3\times {10}^{17}Hz$