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ELECTROMAGNETIC WAVES — Physics STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 SciencePhysicsELECTROMAGNETIC WAVES2 Marks
Question
Write a brief history of Electro Magnetic waves.
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Answer

→Danish physicist Hans Christian Oersted was the first one to discover / notice that moving charges or Electric Current creates / produces magnetic field.
→Faraday discovered that emf and current is induced in a conductor, if the magnetic flux associated with it changes.
→As per the opinion of James Clerk Maxwell, not only an electric current but also a time-varying electric field generates magnetic field.
→When a capacitor is connected with a time- varying current, magnetic field is created in the region outside the capacitor.
→While applying the Ampere's circuital law to find magnetic field at a point outside capacitor, he found an inconsistency in the law. →To remove the inconsistency he suggested existence of an additional current, called by him, the 'displacement current.'
→Maxwell formulated a set of equations involving electric and magnetic fields, and their sources, the charge and current densities.
→These equations are knwon as Maxwell's equations.
→The most important prediction to emerge from maxwell's equations is the existence of electro-magnetic waves, which are (coupled) time-varying electric and magnetic fields that propogate in space.
→The speed of the waves, according to these equations, turned out to be very close to the speed of light $\left(3 \times 10^8 m / s \right)$. This led to a remarkable conclusion that light is an electro magnetic wave.
→Thus, Maxwell unified the domains of electricity, magnetism and light.
→In 1885, Hertz experimentally demonstrated the existence of electro magnetic waves. Their technological use has led to a revolution in the field of communication.

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