________________
(b)
4.
limited to a very small part of this specturm covering the waves with wavelengths of 4000 Å 8000 Å, which we recognize as visible light. Our eyes do not respond to the electromagnetic radiations out side this range. Modern's A.B.C. of Physics, by Satish K. Gupta, pp. 737, 738— Electromagnetic Spectrum 1. Gamma Rays---Highly energetic radiations. 2. X-rays have frequencies in the range 1016 to 3 x 1019 Hz.
X-rays possess a high penetrating power. 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. The frequency of ultra-violet rays lies in the range of 8 x 1014 to 1016 Hz. Visible light. It forms a very narrow part of the electromagnetic spectrum and its frequency ranges from 4 x 1014 to 8 x 1014 Hz. The visible light is emitted due to the atomic excitation. Human eye is sensitive to only visible
part of the electromagnetic spectrum. 5. Infra red rays. Infra-red rays were discovered by Herschell.
Infra-red rays are heat radiation and therefore all hot bodies are the sources of infra-red rays. About 60% of the solar radiation is infrared in nature. The frequency range of infrared rays is 103 - 4 x 104 Hz. Microwaves. The microwaves are produced by oscillating electronics circuits. The frequency of microwaves lies between 1019 - 3 x 10" Hz Hz. The microwaves are used in radar and other communication systems. Radiowaves. Like microwaves, radiowaves are also produced by oscillating electronic circuits. The frequency of radiowaves varies from a few Hz to 1019 Hz. The radiowaves are used as carrier waves in radio broadcasting and TV transmission.
116
Jain Educationa International
For Personal and Private Use Only
www.jainelibrary.org
