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The sun emits radiation of different wavelengths. Some of the solar radiation are visible like those making up the colours of rainbow. Beyond these are radiation in the ultraviolet (UV) and infrared, which are invisible. Visible spectrum normally distributed between 400nm ~ 730nm while wavelength above 730nm are infrared and below 400nm are ultraviolet. UV radiation can be broadly subdivided into UV-A(315 ~ 400), UV-B(280 ~315) and UV-C(100 ~280) in which UV-B(280 ~315) is the main cause of skin damage. |