The energy of the em waves is of the order of 15keV. To which part of the spectrum does it belong?

$\text{ As }\mathrm{\lambda }=\frac{\mathrm{hc}}{\mathrm{E}}$

Where the symbols have theri usual meanings.

$\text{ Here, }E=15\mathrm{keV}=15\times {10}^3 \mathrm{V}$$\text{ and }\mathrm{hc}=1240\mathrm{eVnm}$

$\therefore \mathrm{\lambda }=\frac{1240\mathrm{eVnm}}{15\times {10}^3\mathrm{eV}}=0.083\mathrm{nm}$

As the wavelength range of X -rays is from 1 nm to ${10}^{-3}$ so this wavelength belongs to X -rays.