Write source of ultraviolet rays and uses.

Explanation

Ultraviolet radiation are produced by special type of lamps and very hot bodies.
The Sun is also an important source of UV radiation.
Most of ultraviolet rays coming out of the sun are absorbed in Ozone layer which are at height of 40 - 50 km.
Excess of ultraviolet light is harmful for human body. When body is exposed to UV light for longer time period, melanin is produced in the body hence skin become dark.
Spark produced during welding contain lot of UV light hence to protect eyes special type of face mask are used which contain black coloured glass.
UV radiation is absorbed by ordinary glass. Hence one cannot get tanned or sunburn through glass windows.
Uses :
(i) Ultraviolet waves have very short wavelength (400 nm to 0.6 nm) hence it can be focused into very narrow beam of high precision. It is used in LASIK (Laser Assisted in Situ Keratomleusis).
(ii) In some water purifiers UV bulb is used to kill germs.
(iii) In atmosphere ozone layer work as protective layer. In some region depletion of ozone layer (Due to use of CFC chloroflouro carbon) is matter of concern internationally.