Question

The energy of an $EM$ wave is of the order of $15$ $keV$. To which part of the spectrum does it belong?

• A. Ultraviolet rays
• B. $\gamma$-rays
• C. $X$-rays
• D. Infrared rays

Answer 1

The correct option is C $X$-rays

$\lambda =\frac{hc}{E}$
Here, $E$= $15KeV$
$hc$ = $1240eV$ $nm$
$\mathrm{\therefore \; \lambda }=\frac{1240eVnm}{15\times {10}^{3}eV}=0.083nm$
As the wavelength range of $X-$rays is from 1 $nm$ to ${10}^{-3}n\mathrm{m,}$ this wavelength belongs to the $X-$rays part of the spectrum.