By Bad Seed
By B4D B0YZ 420
By Angel Decoy
Ultraviolet rays are invisible rays that come mainly from the sun, although they can also come from man-made sources such as tanning beds and welding torches.
In terms of energy, UV rays straddle the border between ionizing and non-ionizing radiation. They have more energy than visible light, but not as much as x-rays. Ultraviolet rays often have enough energy to damage the DNA in cells, which means they can cause cancer. But because they don't have enough energy to penetrate deeply into the body, their main effect is on the skin.
Most skin cancers are a direct result of exposure to the UV rays in sunlight. Both basal cell and squamous cell cancers (the most common types of skin cancer) tend to be found on sun-exposed parts of the body, and their occurrence is related to lifetime sun exposure. The risk of melanoma, a more serious but less common type of skin cancer, is also related to sun exposure, although perhaps not as strongly.
While UV rays make up only a tiny fraction of the sun's wavelengths, they are mainly responsible for the damaging effects of the sun on the skin.
Scientists often divide UV radiation into 3 wavelength ranges:
UVA rays are the weakest of the ultraviolet rays. They can cause skin cells to age and can cause some indirect damage to cells' DNA. UVA rays are mainly linked to long-term skin damage such as wrinkles, but are also thought to play a role in some skin cancers.
UVB rays are slightly stronger. They are mainly responsible for direct damage to the DNA, and are the rays that cause sunburns. They are also thought to cause most skin cancers.
UVC rays are the strongest UV rays. Fortunately, because of this, they react with ozone high in our atmosphere and do not reach the ground. Therefore UVC rays are not present in sunlight and are not normally a risk factor for skin cancer. But they can be found in some man-made sources, such as arc welding torches and mercury lamps.