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Postby TGTS0907129» Electromagnetic waves theory

Explain the theory of electromagnetic waves

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A knowledge of electromagnetic wave theory is so important or an understanding of modern physics that the next chapter has been devoted to a discussion of these waves. However, since electromagnetic waves are produced by electric oscillations, it is appropriate that we consider them briefly in that context here. In an oscillating electric circuits the varying alternating current produces correspondingly varying magnetic and electric fields. These fields are at right angles to each other and travel out into space with the speed of light, approximately 18(6,)000 mi/s, or 3.00 × 108 m/s. This radiation of energy into space is facilitated by connecting the circuit to a suitable antenna that is comparable in size with the wavelength of the radiation. These electromagnetic waves were investigated in 1887 by Hertz and are sometimes called Hertzian waves.

One set as “sending” station and a similar set as a “receiving” station. He produced “standing” electromagnetic waves and was able to measure the distance between adjacent nodes and thus determines the wavelength. Since the frequency of the oscillating circuit was known, he was able to measured the speed of the electromagnetic waves from the wave equation v = fλ. His measurement

His measurement showed that this speed was the same as that for the speed of light. The Italian scientist Marconi (1874-1937) applied the discoveries of Hertz to the field of electrical communication. His researches began the radio age that has been so fruitful in the communication industry.

A remarkable contribution to electromagnetic theory was made by the British mathematical physicist Maxwell. In 1864 he had shown that an oscillating electric circuit should be a source of electromagnetic waves that should travel with a speed related to the magnetic permeability and electric permittivity of the transmitting medium. The speed is given by the equation
                               


When the values of μ  and ε  for free space are inserted the value of v comes out equal to the accepted value for the speed of light in empty space.
 

By TGTT30071258 on 12/23/2015 12:31:49 AM
TGTS0907129 on 12/8/2015 3:29:45 AM
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