The sun produces light with wavelengths between 200 nm and 2600 nm, similar to a 5250°C blackbody. Light is categorized into ultraviolet (200-400 nm), visible (400-700 nm) and infrared (700 nm - 1 mm). As light passes through the atmosphere, gases absorb certain wavelengths - ozone absorbs below 290 nm while water vapor absorbs infrared bands. The maximum intensity is at 480 nm, with ultraviolet containing 7% of total energy and infrared containing 45.7% of the energy from the sun.

1. Solar radiation spectrum
• The sun produces light with wavelengths in
the range of about 200 nm to 2600 nm. It is
similar to a 5525 K (5250 °C) blackbody,
which is approximately the temperature at the
surface of the sun.
• Wavelength of ultraviolet (UV) rays ranges
from 200 to 400 nm, visible light: 400 nm
(violet) to 700 nm (red) and the infrared (IR):
700 nm to 1mm.
• As light passes through the atmosphere, some
is absorbed by gases with specific absorption
bands.
• Ozone molecules absorbs almost completely
the short wave radiation below 0.29 µm. Thus
the shortest wavelength that reaches the
Earth’s surface is approximately 0.29 µm.
• Water vapour absorbs mainly the IR bands.
• Maximum intensity occurs at wavelength of
480 nm.
• Radiation having wavelength ranging from 0
to 380 nm, 380 to 780 nm and 780 to 4000 nm
contains 7, 47.3 and 45.7 % of total energy in
the radiation.
Solar spectrum
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