Content area
Full Text
The sun emits ultraviolet (UV) radiation in the range of 100- 400nm in addition to visible radiation. The UV radiation is banded for convenience in to UVC (100-280nm), UVB (290-320) and finally UVA (320-400nm) with the longer wavelengths of light (380-770nm) representing the visible portion of the spectrum. Sunlight is composed mainly of UVA (as much as 90 per cent) with the remainder consisting of UVB radiation. Most UVC is filtered out by the ozone layer.