The Sun

Radiation

The sun provides the earth with life-giving energy and is the major factor in determining the earth’s climate and weather. The sun not only sends visible light to the earth but also invisible radiation that can have a negative impact on our health if received in doses which are too high.

Solar radiation consists of a broad variety of rays. Some don’t even reach the earth as they are blocked by the ozone layer. Radiation that reaches the earth consists of visible rays, infrared rays (IR) and ultraviolet rays (UV). UV radiation is further divided into UVA, UVB and UVC rays, depending on their wavelength. UVC rays are also blocked by the ozone layer.

Radiation chart

Visible light

Visible light comprises all the colours we see with the naked eye.

Infrared (IR) rays

Infrared (IR) rays transport heat energy, enabling us to experience heat.

Ultraviolet (UV) rays

Ultraviolet (UV) rays are invisible and are divided into UVA, UVB and UVC rays. UVA rays cause long-term skin damage, including skin cancer and premature skin aging, while UVB rays are the main cause of sunburn. Approximately 10 times more UVA rays reach the earth surface than UVB rays. UVC rays are absorbed by the earth's atmosphere and don’t affect the skin.

The intensity of sun radiation is dependent on several factors, including the time of year, time of day, latitude, altitude, ground reflections and weather conditions. The sun is brighter at midday, for example, and at high altitudes less UV radiation is absorbed by the thinner atmosphere.

Did you know?


80% of UV rays can penetrate clouds.	Clean snow reflects up to 80% of all UV rays.	60% of UV rays occur between 10 am and 2 pm.	UV radiation increases by 4% with each 300 metres in altitude.

Shade can reduce UV exposure by 50% or more.	At half a metre under the water, UV is still 40% as intense as on the surface.	White sand reflects up to 15% of UV rays.	Water reflects about 25% of UV radiation.