Pratiyogita Darpan Extra Issue Series-2 General Studies Geography (India And World)

Pratiyogita Darpan Extra Issue Series-2 General Studies Geography (India And World)
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Pratiyogita Darpan Extra Issue Series-2 General Studies Geography (India And World)

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and the lowest energy content. THERMAL RADIATION Every object which is at a temperature above Absolute Zero 273 16 C radiates photons of all kinds. The average energy of the photons emitted increases with the temperature. We experience this heat during the peak period noon in visible light radiation. But even objects which are not hot enough to glow like the sun still radiate quantities of infra red radiation, for instance, our own bodies. The body temperature, that is, cool bodies, radiate micro waves and longer radio waves. These radions, called thermal radiations , can indicate the temperature levels of the objects emitting them. RADIO WAVES Radio waves are the radiations with the longest wavelengths, that is from 50 centimetres to as much as 30 metres. Objects in outer space that emit such radiations are called Radio Sources . WINDOWS ON OUTER SPACE The atmosphere of the earth is like a sieve which allows only some
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wavelengths from outer space to reach us. Sunlight forms one group of wavelengths which come down through the atmosphere. This includes not only the visible light but also a port of the invisible light, namely, the near ultraviolet 400 to 300 nanos and the near infrared 700 to 2500 nanos . This is one of the windows that opens out on outer space. MICRO WAVE WINDOW The other window is called the micro-wave window . This window covers all wavelengths from one millimetre to 30 metres. The existence of the microwave window was not particularly noticed or studied till 1932 when Karl Jansky of the Bell Telephones announced that he had