________________
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 10 ms-1. 2. They also obey the laws of reflection and refraction. 3. They can also undergo interference and can be polarised. 4. When allowed to fall on metals, they cause the emission of
photoelectrons. 5. They can affect a photographic plate. 6. Ultra-violet rays can cause flourescence in certain materials (Tube
Lights) 7. Ultra-violet rays can not pass through glass but quartz, and rock
salt are transparent to them. 8. Ultra-violet rays possess the property of synthesizing vitamin D,
when the skin is exposed to the sunlight. 59. Ibid., p. 740
X-RAYS The discovery of X-rays was accidentally made by a German professor Rontgen in 1895. In laboratory, X-ray can be produced by using Coolidge X-ray tube. Properties. X-rays have the following properties: 1. X-rays are electromagnetic waves of very short wavelength ranging
from 0.01 Å to 10 Å. 2. X-rays travel in vacuum with the speed of light (3 X 10m s-1), as
they are also electromagnetic waves.
They are not deviated by electric and magnetic fields. 4. They, affect the photographic plate very intensely. 5. They ionise the gas through which they pass.
They cause fluorescence in substances like zinc sulphide, barium platinocyanide, calcium tungstate, etc.
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TAHU UFI 3106 120-121
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