Gujarat BoardEnglish MediumSTD 12 SciencePhysicsELECTROMAGNETIC WAVES2 Marks
Question
Write a short note on Ultra violet rays.
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Answer
$\rightarrow$ Wave length range: from $4 \times 10^{-7} m \ (400 \ nm)$ to $6 \times 10^{-10} m \ (0.6 \ nm)$
$\rightarrow U.V. ($or $UV)$ radiation is produced by special lamps and very hot bodies.
$\rightarrow UV$ light in large quantities has harmful effects on humans.
$\rightarrow$ Exposure to $UV$ radiation induces the production of more melanin, causing tanning of the skin, which is known as Sunburn.
$\rightarrow$ The Ozone layer in the atmosphere at an altitude of about $40-50 \ km$ absorbs the $UV$ rays coming from the sun. In this way, it acts as a protecting shield for humans. Depletion of Ozone layer by chlorofluoro carbons $(CFCs)$ gas $($such as freon$)$ is a matter of concern.
$\rightarrow$ Welders wear special glass goggles or face masks with glass windows to protect their eyes from large amount of $UV$ produced by welding arcs. $($Because $UV$ radiation is absorbed by ordinary glass.$)$
$\rightarrow UV$ radiations can be focused into very narrow beams for high precision applications such as $ \text{LASIK} ($Laser assisted in situ keratomileusis.$)$ eye surgery.
$\rightarrow UV$ lamps are used to kill germs in water purifiers.
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