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Infra-red rays obey laws of reflection and refraction. Infra-red rays can produce interference and can be polarised. When allowed to fall on matter, infra-red rays produce an increase in temperature. . Infra-red rays affect a photographic plate. When absorbed by molecules, the energy of infra-red rays gets converted into molecular vibrations. They are scattered less as compared to the visible light by the atmosphere. Hence, infra-red rays can travel through longer distances through atmospehre under the conditions of smoke, fog, etc. Nitrogen and oxygen gases are found to be transparent
medium to all the wavelengths of infra-red rays. Applications : 1. Infra-red rays from the sun keep the earth warm and hence help
to sustain life on earth. 2. The coal deposits in the interior of earth are the result of
conversion of forest wood into coal due to infra-red rays. Infra-red rays are used in solar water heaters and cookers. Infra-red rays photographs are used for weather forecasting. Infra-red rays are used for taking photographs during the conditions of fog, smoke, etc. Infra-red rays absorption spectra is used in the study of molecular
structure and then to check the purity of the chemicals. 7. Infra-red rays are used for producing dehydrated fruits. 8. Infra-red rays are used to provide electrical energy to satellites
by using solar cells. 9. Infra-red rays are used to treat muscular strains. 58. Ibid., p. 740
“Ultra-Violet Rays Ultra-violet rays were discovered by Ritter in 1801. The ultra-violet rays are part of solar spectrum. They can be produced by the arcs of mercury and iron. They can also be obtained by passing discharge through hydrogen and xenon. Properties : 1. Ultra-violet rays are electromagnetic waves and travel with the
speed of 3 x 108 ms-1.
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