As it turns out, nearly 70% of the total energy in the sun’s radiant electromagnetic energy (everyday light) is in the ultraviolet (UV) range of the spectrum (see Figure 2). Much of this UV energy would be invisible to us if it hadn’t been filtered out by the atmosphere, which consists mostly of gases that absorb UV radiation.
UV radiation is also a form of ionizing radiation and is capable of breaking chemical bonds and ionizing atoms and molecules. This is the underlying mechanism of medical X-ray imaging. UV radiation can damage living tissue and cause burns, especially to the skin.
The spectrum of light of wavelength 400-700 nm is called short-wave ultraviolet (UV-A), and long-wave ultraviolet (UV-B) radiation penetrates the ozone layer in the atmosphere and reaches the Earth’s surface. UV-A is responsible for the majority of sunburns, eye damage, and skin cancer. UV-B does the fun stuff like create rashes and speed up melanoma. The wavelengths of UV-A are 315-400nm while UV-B wavelengths are 400-315nm.
Frequency is measured in hertz (Hz) and is a number from zero to infinity (called an integer). A good way to think about the hertz is big, small, very large (Hertz is also sometimes written with a single letter e, where e = 10-8.) One Hertz (Hz) is exactly one complete oscillation of the wave. The number one (1) Hertz is a wave that moves one cycle in 1 second of time. This means that all wavelengths are multiples of 1 Hertz. A Hertz is anything bigger than 1. d2c66b5586