Microwave spectroscopy is used to probe transitions between rotational energy levels in molecules.
(a) A typical wavelength for microwaves is 10-2 m, compared with 10-5 m for infrared radiation. Is the energy separation between rotational energy levels in a molecule greater or less than the separation between vibrational energy levels?
(b) Microwave ovens cook food by heating the water in the food. Absorption of microwave radiation by the water excites it to a higher rotational energy state, and it gives off this excess energy as heat when it relaxes to its ground state. Why are vibrational and electronic energy states not involved in this process?