Most natural UV light comes from the sun. Only 10 % of sunlight is UV, and only one-third of it gets through the atmosphere.

UV light comes from the sun and is transmitted in waves or particles at different wavelengths an frequencies.

Some skin conditions can be treated using UV light.

EM is the broad range of wavelengths. It is divided into seven regions and ordered in decreasing wavelength and increasing energy and frequency, namely radio waves, microwaves, infrared (IR), visible light, ultraviolet (UV), X-rays and gamma-rays.

Substances like minerals, plants, fungi, microbes, and organic and inorganic chemicals, can absorb UV radiation, causing electrons to jump to a higher energy level. When the electrons return to a lower energy level, they emit a portion of the absorbed energy as visible light.

UV radiation has enough energy to break chemical bonds. UV photons can cause ionization, meaning chemical bonds will break that otherwise would not.

• UVA, or near UV (315-400 nanometers)
• UVB, or middle UV (280-315 nanometers)
• UVC, or far UV (180-280 nanometers)

A suntan is a reaction to exposure to UVB rays. When the body senses sun damage, it sends melanin, a pigment in the body, to absorb UV light and protect the body from more damage, resulting in a darkened skin.