The terminology of different parts of the electromagnetic spectrum is given in the text.

Energy of a photon is given as:

$E=h v=\frac{h c}{\lambda}$

Where,

h = Planck’s constant = 6.6 × 10−34 Js

c = Speed of light = 3 × 108 m/s

λ = Wavelength of radiation

$\therefore E=\frac{6.6 \times 10^{-34} \times 3 \times 10^{8}}{\lambda}=\frac{19.8 \times 10^{-26}}{\lambda} \mathrm{J}$

$=\frac{19.8 \times 10^{-26}}{\lambda \times 1.6 \times 10^{-19}}=\frac{12.375 \times 10^{-7}}{\lambda} \mathrm{eV}$

The given table lists the photon energies for different parts of an electromagnetic spectrum for differentλ.

The photon energies for the different parts of the spectrum of a source indicate the spacing of the relevant energy levels of the source.