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Electromagnetic (EM) radiation consists of coupled electric and magnetic fields oscillating in directions perpendicular to each other and the direction of propagation of radiation. EM radiation can be an interesting probe to study materials’ properties. It is the electric field component of EM radiation that interacts with molecules and solids in most cases. Two conditions need to be fulfilled for the absorption of EM radiation during such interaction: (i) the energy of a quantum of EM radiation must be equal to the separation between energy levels in the atom/molecule, (ii) the oscillating electric field component must be able to stimulate an oscillating electric dipole in the atom/molecule. EM radiation in the microwave region of the EM spectrum can interact with molecules having a permanent electric dipole moment created by molecular rotation. On the other hand, infrared radiation would interact with molecules in vibrational modes giving rise to a change in the electric dipole moment.