UV radiation also known as ultraviolet radiation is one form of energy coming from the sun. Ultraviolet radiation is a form of electromagnetic radiation, the main source of UV radiation is the sun, although it can also come from man-made sources such as tanning beds and welding torches. Continuous thermonuclear reactions in the sun’s core yield a wide spectrum of electromagnetic energy that radiates through space in all directions. This radiant energy is called electromagnetic because it is in the form of oscillating electric and magnetic fields. Electromagnetic radiation exhibits both wavelike ( oscillating field) and particle like (discrete packet ) properties. These discrete packets or quanta are called photons. Even though you may have only just started hearing about UV and the effects it has on you, it is nothing new. In fact, UV is as old as the earth itself. Cloudy days deceive many people into thinking the danger of UV radiation is minimal. Clouds affect the strength of radiation reaching the ground in complex ways. Most clouds block some UV radiation, but the degree of protection depends on the type and amount of cloud. Some clouds can increase the UV intensity on the ground by reflecting and refracting the sun's rays. People can also be caught unawares when a small break in an overcast deck of clouds allows a brief burst of intense radiation to reach the ground. Cold air can also be deceptive as the temperature is not directly related to UV intensity. Skiers should take particular care as reflective snow on the ground, and high altitude raises the UV Index significantly relative to its value at sea level. UV is particularly useful in creating vitamin D, which is a group of vitamins found in liver and fish oils, essential for the absorption of calcium and the prevention of rickets in children and osteomalacia in adults. They include calciferol ( vitamin D2 ) and cholecalciferol ( vitamin D3 ). Radiation is the emission of energy from any source. There are many types of radiation.Radiation exists across a spectrum from very high-energy radiation – like x-rays and gamma rays – to very low-energy radiation – like radio waves. UV rays have more energy than visible light, but not as much as x-rays. Higher energy UV rays often have enough energy to remove an electron from an atom or molecule, making them a form of ionizing radiation. Ionizing radiation can damage DNA in the cells in our body, which in turn may lead to cancer. However, because UV rays do not have enough energy to penetrate deeply into the body, their main effect is on the skin. Scientists often divide UV radiation into three wavelength ranges. UVA rays are the weakest of the UV rays. They can cause skin cells to age and can cause some indirect damage to cells’ DNA. UVA rays are linked to long-term skin damage such as wrinkles but are also thought to play a role in some skin cancers. UVB rays have slightly more energy than UVA rays. They can damage the DNA in skin cells directly, and are the main rays that cause sunburns. They are also thought to cause most skin cancers. UVC rays have more energy than the other types of 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 normally a risk factor for skin cancer.However they can also come from some man-made sources, such as arc welding torches, mercury lamps, and UV sanitizing bulbs that kill bacteria and other germs such as in water, air, food, or on surfaces.