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Ultraviolet rays were discovered by J. Ritter (1776-1810) in 1801.
Ultraviolet rays were discovered by J. Ritter (1776-1810) in 1801.
They can be produced by the mercury vapour lamp, electric spark and carbon arc lamp.
They can be produced by the mercury vapour lamp, electric spark and carbon arc lamp.
They can also be obtained by striking electrical discharge in hydrogen and xenon gas tubes.
They can also be obtained by striking electrical discharge in hydrogen and xenon gas tubes.
The Sun is the most important natural source of ultraviolet rays, most of which are absorbed by the ozone layer in the Earth’s atmosphere
The Sun is the most important natural source of ultraviolet rays, most of which are absorbed by the ozone layer in the Earth’s atmosphere
Properties
Properties
1) They produce fluorescence in certain materials, such as 'phosphors'.
1) They produce fluorescence in certain materials, such as 'phosphors'.
2) They cause photoelectric effect.
2) They cause photoelectric effect.
3) They cannot pass through glass but pass through quartz, fluorite, rock salt etc.
3) They cannot pass through glass but pass through quartz, fluorite, rock salt etc.
4) They possess the property of synthesizing vitamin D, when skin is exposed to them.
4) They possess the property of synthesizing vitamin D, when skin is exposed to them.
Uses
Uses
1) Ultraviolet rays destroy germs and bacteria and hence they are used for sterilizing surgical instruments and for purification of water.
1) Ultraviolet rays destroy germs and bacteria and hence they are used for sterilizing surgical instruments and for purification of water.
2) Used in burglar alarms and security systems.
2) Used in burglar alarms and security systems.
3) Used to distinguish real and fake gems.
3) Used to distinguish real and fake gems.
4) Used in analysis of chemical compounds.
4) Used in analysis of chemical compounds.
5) Used to detect forgery
5) Used to detect forgery
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