The terminology different parts of the electromagnetic spectrum is given in the text. Use the formula E = hv (for energy of a quantum of radiation : photon) and obtain the photon energy in units of eV different parts of the electromagnetic spectrum. In what way are the different scales of photon energies that you obtain related to the sources of electromagnetic radiation ?

Explanation

Photon energy [for `lamda =1` m]
`=(6.63xx10^(-34) xx3xx10^(8))/(1.6xx10^(-19)) eV=1.24 xx10^(-6) eV`
Photon energy for other wavelengths in the figure for electromagnetic spectrum can be obtained by multiplying approximate powers of ten. Energy of a photon that a source produces indicates the spacings of the relevant energy levels of the source. For example, `lamda = 10^(-12) m` corresponds to photon energy `= 1.24 xx 10^(6) eV = 1.24 MeV`. This indicates that nuclear energy levels (transition between which causes γ-ray emission) are typically spaced by 1 MeV or so. Similarly, a visible wavelength `lamda = 5 xx 10^(-7)` m, corresponds to photon energy = 2.5 eV. This implies that energy levels (transition between which gives visible radiation) are typically spaced by a few eV.