Light coming from the sun is a magical source of energy for us, and we can not survive on earth without the light rays coming from the sun. The light rays that reach  ground are not homogenous, but they comprise of many wavelengths of light. The wavelength of light that fall between the range of 400nm – 100 NM is called ultraviolet rays. UV rays are further classified in mainly three groups known as UV-A, UV-B and UV-C rays. UV-A rays have wavelength in the range of 400 nm – 320 nm, UV-B rays have wavelength in the range 320nm-280nm and UV-C rays have wavelength in the range of 280 nm – 100nm.

UV-C rays never reach  earth and absorb by the atmosphere mainly in the ozone layer. Only a few percentage of UV-B rays reaches  earth along with most part of the UV-A rays. The UV-A and UV-B rays that reach to land are seriously harmful to skin, if your skin exposed to them for a longer time. UV-B rays are absorbed by the upper dead layer of the skin and cause sunburn while UV-A rays penetrate the skin deep inside and cause problems like wrinkles, loss of elasticity and premature aging. These rays are also harmful to our eyes.

What is Sunburn:

It is the most common result of UV exposure to skin. When high energy UV rays hit the cells of skin, our skin cells absorb this energy and get damage. The body tries to repair damaged cells and remove dead cells by sending fresh blood supply to these areas of skin. This additional supply of blood results in redness on that area. There are evidences that sunburn can cause DNA damage. Also, numerous and prolonged exposure to the sun can cause skin cancer so you should always avoid prolong exposure to sun.

The period in which a person get sunburn depend on the intensity of UV ray and the skin-type of the person. A compound called melanin found in the skin is resistance to UV rays. Black people inherit high volume of melanin and thus their opposition to sunburn is high compared to fairer people. So black people get sunburn their skin after a very long exposure to sunlight compared to the fairer people who see redness on their skin because of sunburn darned quickly.