Ultraviolet LightAll energies that move at the speed of light are referred to as electromagnetic radiation or 'light'.

Electromagnetic Spectrum

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*Ultraviolet light has shorter wavelengths than visible light.

*Scientists have divided the ultraviolet part of the spectrum into three regions: the near ultraviolet, far ultraviolet, and extreme ultraviolet. The three regions are distinguished by how energetic the ultraviolet radiation is.

The Sun

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Our Sun gives off light at all the different wavelengths in the electromagnetic spectrum, but it is ultraviolet waves that are responsible for causing our sunburns and skin cancer. This is the sun taken at an Extreme Ultraviolet wavelength. Some ultraviolet waves from the Sun penetrate Earth's atmosphere but most of them are blocked from entering by many gases like Ozone.

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This false-color picture shows how the Earth glows in ultraviolet (UV) light.

The part of the Earth facing the Sun reflects much UV light.

Visibility

• Ultraviolet waves are invisible to the human eye • Some insects can see them: bumblebees, Many fish,

amphibians, reptiles, birds, and some mammals use UV vision for such basic activities as foraging, mate selection, and communication.

• Consequently, for humans, all hues can be produced by mixing red, green and blue light. This is how a color t.v. works. A mixture of three wavelengths produces several million apparent colors. It is difficult to vision more dimensions than three but animals with 4 and 5-dimensional color vision exist.

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Sources

http://science.hq.nasa.gov/kids/imagers/ems/uv.html

http://www.nas.nasa.gov/About/Education/Ozone/radiation.html

http://en.wikipedia.org/wiki/Ultraviolet

http://www.bio.bris.ac.uk/research/vision/4d.htm

http://csep10.phys.utk.edu/astr162/lect/light/spectrum.html