ABSTRACT
The Sun is the universal source of energy in the biosphere. During the nuclear fusion processes
occurring in the Sun, matter is changed into energy, which is emitted into space in the form of
electromagnetic radiation, having both wave and particle properties. The electromagnetic radiation
has a spectrum or wavelength distribution from short wavelength (1026 nm, g-and x-rays) to long wavelength (1015 nm, long radio waves). About 99% of the Sun radiation is in the wavelength
region from 300 to 4000 nm and it is called the broadband or total solar radiation. Within this
broadband, different forms of energy exist, which can be associated with specific phenomena
such as harmful and potentially mutagen ultraviolet radiation (UV 100-400 nm), sight (visible
light 400-700 nm), and heat (infrared radiation 700-4000 nm). The particles producing the elec-
tromagnetic waves are called photons or quanta. The energy of a photon or quantum can be
expressed as hn, where h is the Planck’s constant (6.626 10234 J sec) and n is the frequency of the photon. The frequency is in turn equal to cl21, where c is the speed of light (3 108 m sec21) and l is the wavelength of the photon in nanometres (nm). According to this formula the shorter the photon wavelength, the higher its energy; for example, the energy of one photon of 300 nm
light is 6.63 10219 J, the energy of one photon of 400 nm light is 4.97 10219 J, the energy of one photon of 700 nm light is 2.84 10219 J, and the energy of one photon of 4000 nm light is 0.49 10219 J.
