3 x 10^8

Another interesting stuff about light or rather electromagnetic waves. We all know they all travel at a constant speed of 3 x 10^8 m/s in vacuum. But do you know why?

Electromagnetic induction and Law of Conservation of Energy. As we know a changing magnetic field leads to an electric field or a voltage. Symmetrically, a changing electric field will lead to magnetic field. Electromagnetic waves are made of magnetic field and electric field oscillating perpendicularly to each other. The changing electric field generates maintains the changing magnetic field, and it maintains the changing electric field in turn. If the speed decelerates, one of the changing field is unable to maintain the other, ie a slowing down electric field generates a weaker magnetic field and the latter generates a weaker electric field. The wave will eventually die. If the speed is accelerating, intensity of each field will get higher and this defies Law of Conservation of Energy. Both fields have to come to a constant speed in order to maintain each other. This speed is 3 x 10^8 m/s.

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