Solar Electromagnetic Radiation

Visible Light

Energy received on Earth from the visible part of the Sun's electromagnetic spectrum provides the energy for practically every process on the planet's surface, including life itself.

Sunlight provides the energy:

to create the motions (winds) of the Earth's atmosphere and drive the ocean currents.
required for all photosynthetic processes and is therefore responsible for all food on the planet.
to drive the Earth's water cycle.
to run our industries, heat our homes, and provide electricity¹ for light and communications.
¹The only energy we use that is not from the Sun is a very small amount of our energy from nuclear and geothermal sources.

Ultraviolet

The Sun's high temperature means that it also produces a significant amount of light in the ultraviolet (uv) part of the electromagnetic spectrum. Most solar uv light is absorbed by the Earth's ozone layer or reflected back into space. Only a small portion of the uv which reaches the Earth in space actually reaches the surface of the Earth.

Solar uv radiation is subdivided into three wavelength bands; UVA (315-400 nm), UVB (290-315 nm) and UVC (220-290 nm).

UVA radiation is important in the generation of photochemical smog and also in fading and damage to plastics, paints and fabrics.
UVB makes up about 1% of solar uv band, most of which is absorbed by Earth's ozone layer. Nevertheless, the uvB region is of particular interest because the uv photons at this wavelength can cause damage at the molecular level within a living cell. Relatively small changes in thickness of the ozone layer can lead to significant changes in amount of uvB radiation reaching the Earth's surface.
UVC is totally absorbed by ozone and other gases, and does not reach the Earth's surface.

X-rays and other high energy photons are filtered out of the solar spectrum by the Earth's upper atmosphere so that no ionizing radiation from the Sun reaches the Earth's surface.

[Home]

Prepared by the YES I Can! Science Team,