Ultraviolet light is organized from the shorter (and higher energy) wavelength (UVC) to the longer (and lower energy) wavelength (UVA). Each UV type has its own location on the electromagnetic spectrum. UVC energy range is 200-280 nm, UVB range is 280-320 nm, UVA2 is from 320-340, and UVA1 from 340-400nm. Visible light is 400-780 nm.

Typically, the longer the wave, the less harmful it is to humans exposed to its energy; the shorter the wave, the more intense. Each has a beneficial purpose. For instance, while UVC is the most powerful of ultraviolet rays and considered harmful to humans, hospitals use germicidal lamps with UVC (253.7 nm) to sterilize surgical instruments, water and the air in operating rooms because it can destroy bacteria and viruses.

People primarily are exposed to UVA and UVB light when spending time in the sun. UVC rays are generally filtered out by the earth’s ozone layer. Some scientists hypothesize that erosion of the ozone layer may allow some UVC rays to reach the earth, but the research has not been conclusive.

UVA waves are longer than other ultraviolet waves and can penetrate the skin to the deeper layers, known as the dermis. While it is possible to darken only existing pigment with UVA alone, this can only be accomplished by exposure to high amounts of UVA, which may have long term effects.

UVB waves are shorter than UVA waves, principally affecting the upper layers of the skin called the epidermis. UVB waves stimulate the upper layers of the skin to produce melanin, the pigment that forms a coating around other skin cells to protect them from overexposure to the sun. This process is known as pigmentation. Although UVB cannot penetrate the skin as deeply as UVA, it is more likely than UVA to cause sunburn.

A good tanning lamp needs a balance of UVA and UVB. UVB stimulates melanin production and can burn the skin if overexposed; UVA2 acts a lot like UVB, with melanin production and some pigment darkening; it is also closely associated with elastosis (photoaging, wrinkles). UVA1 penetrates deeper past the surface of the skin and is primarily responsible for pigment darkening. Newer lamps such as the Bronzing Sun HPK90 focus on providing enough UVB to stimulate the melanin and aid in production of vitamin D, plenty of UVA1, and less of UVA2. This combination results in robust pigmentation, very effective pigment darkening and a natural protection against damage from the sun.

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