Light is electromagnetic radiation with electric and magnetic fields. Ultraviolet light has a shorter wavelength, higher frequency, and higher energy than visible light. UVA, UVB, and UVC classify ultraviolet light by wavelength and energy. Most UV light is absorbed by the ozone layer, but UVA causes tanning and sunburn and is essential for vitamin D production. UVB causes skin cancer and premature aging.
Light is made up of energy waves that are able to move without the presence of a medium to travel through. Light energy has both electric and magnetic fields, so it is often referred to as electromagnetic radiation. Light waves come in many sizes or wavelengths. The light that we can see is only a very small part of the spectrum of light waves that exist. Ultraviolet light is part of the electromagnetic spectrum beyond visible light.
Humans cannot see ultraviolet light, but some insects, such as bees, can. UV light has a shorter wavelength, higher frequency, and higher energy than light within the visible spectrum. Wavelength is the size of the wave, or the distance between two corresponding points on the waves, such as peak-to-peak or valley-to-valley. Frequency is the number of waves that pass at a certain point during a specific amount of time, usually one second. Frequency is directly related to energy, so the higher the frequency of the wave, the higher the energy and vice versa.
Depending on the frequency of the light, different colors are produced. In the visible spectrum, colors range from red, the lowest frequency of visible light, to violet. Ultraviolet light is so called because it is beyond violet. It has a shorter wavelength than violet light and a higher frequency and energy. X-rays come after UV light on the electromagnetic spectrum.
The spectrum of UV light can be divided in several ways. Scientists refer to near, extreme and far UV light, based on the wavelength of the light and its energy. UVA, UVB and UVC are also used to classify ultraviolet light. Again, the categories are determined by wavelength length and energy. UVA or near-UV light has the longest wavelength and the least energy, while extreme light has the shortest wavelength and the most energy.
Most of the ultraviolet light on Earth comes from the sun. When UV light reaches the atmosphere, it reacts with oxygen molecules to create ozone. This reaction is what causes the ozone layer to form above the Earth. The ozone layer can be anywhere from 31 to 10 miles (50 to 10 km) above sea level. Almost all shortwave ultraviolet light is absorbed by the ozone layer before it can reach the earth’s surface.
Longer wavelength ultraviolet light, or UVA, is able to pass through the ozone layer and continue on to the surface. This type of UV light is what causes tanning and sunburn. These wavelengths are essential for a healthy human life as they cause the production of vitamin D in the body. This in turn is used to form healthy bones and teeth. UV light can also be used to help treat skin conditions, such as psoriasis.
Too much exposure to ultraviolet light will have harmful effects. UVB light causes sunburn and some types of skin cancer. The most dangerous of skin cancers is due to DNA damage to skin cells caused by UVB light. All types of UV light also affect collagen, resulting in premature skin aging.
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