________________
Name
Gamma-rays X-rays
Ultra-Violet rays (UV)
Visible light
Infra-Red rays (IR)
Heat radiation Microwaves
Eelctromagnetic Spectrum
Wavelength range (m)
Frequency range (Hz)
5 x 1020 3 x 1019 3 x 1019 1016
10168 x 1014
8 x 1014 - 4 x 1014
4 x 1014 1013
3 x 10133 × 109
3 x 1011 - 109 -
3 x 109 3 x 108
3 x 108 3 x 107
Ultra High radio Frequencies (UHF) Very High radio Frequencies (VHF) Radio frequencies Power frequencies 60 - 50
1.
3 x 107 3 x 104
6 × 10-13 10-10 1 x 10-10 - 3 x 10-8
3 x 10-8-4 x 107
4 x 10-7 - 8 x 10-7
8 x 10 3 x 10-5
10-5 10-1 10-33 x 10-1
10-1- 1
1 - 10
10 - 104
5 x 1066 x 106
Jain Educationa International
57. Satish K. Gupta, op. cit, p. 739
"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 infra-red in nature. Following are a few sources to produce infra-red rays.
1. Nernst lamp. The filament of Nernst lamp is made from the mixture of ziroconium, thorium and cerium. When a current is passed through such a filament, then at a temperature of about 1200 K, infra-red rays are emitted.
How produced
2. Globar. It is basically a rod of silicon carbide, which when heated to a temperature of about 900 K by passing current, produces infrared rays.
Nuclei of atoms. Bombardment of high Z target by electrons. Excitation of atoms and vacuum spark. Excitation of atoms, spark and are flame.
Excitation of atoms and molecules.
Heating.
Oscillating currents in special vacuum tubes. Oscillating circuits.
Oscillating circuits.
Oscillating circuits. Weak radiation from a.c. circuits.
3. LASER. It is used to produce monochromatic infra-red rays. For example, He-Ne LASER gives infra-red rays of wavelength 0.69 x 10 m, 1.19 × 106 m. and 3.39 × 106 m. CO, LASER provides infra-red rays of wavelength 10.6 x 10 m.
To detect infra-red rays, thermocouples, thermopiles, bolometers, photoconducting cells are used.
Properties :
Infra-red rays are electromagnetic waves and travel with a speed of 3 x 108 ms-1.
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