Question

Calculate the speed of EM wave in a glass slab in which the frequency of EM wave is $4\times {10}^{14}Hz$ and wavelength is$500nm$.

Answer 1

Step 1: Given data

Frequency, $f=$ $4\times {10}^{14}Hz$

Wavelength, $\lambda =$$500nm$

To convert $nm$into $m$:

$1nm={10}^{-9}m$

$\Rightarrow 500nm=500\times {10}^{-9}m$

$\Rightarrow 500nm=5\times {10}^{-7}m$

Step 2: To calculate: Speed (v) of EM wave in a glass slab

Formula used: $Speed=Wavelength\times Frequency$

$\Rightarrow v=f\lambda$

$\Rightarrow v=4\times {10}^{14}\times 5\times {10}^{-7}$

$\Rightarrow v=20\times {10}^7\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s$}\right.$

$\Rightarrow v=2\times {10}^8\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s$}\right.$

Hence, the speed of EM wave in glass slab is$2\times {10}^8\raisebox{1ex}{$m$}\!\left/ \!\raisebox{-1ex}{$s$}\right.$.