As becomes clear from this table, solar radiation is by far the most important energy source for controlling temperature conditions on the surface and near it. Therefore, in this discussion we will ignore all other sources and concentrate entirely on solar radiation. Before proceeding with our discussion of insolation, let's review concepts pertaining to radiation as a form of energy in general. All objects emit some energy in the form of radiation. This energy could be thought of as a wave.
Objects typically emit waves of many kinds at the same time.
Wavelength and frequency Fig. All electromagnetic radiation travels at the same speed. Electromagnetic spectrum Fig. Electromagnetic waves of all wavelengths form a continuum - electromagnetic spectrum. EM radiation can be classified by the wavelength.