The Maxwell Equations: Feynman's Physics Explained

Feynman Vol II9-10

This is the great moment of synthesis. Maxwell noticed the known laws of electricity and magnetism were inconsistent with conservation of charge, and fixed them by adding a new term, the 'displacement current.' That one addition had a stunning payoff: the equations now predicted self-propagating electromagnetic waves traveling at a speed he could calculate — exactly the known speed of light. In a stroke, light was revealed to be an electromagnetic wave.

The big idea

Maxwell's equations united electricity, magnetism, and light.

Think about it

Maxwell calculated a wave speed and it matched the speed of light. Why was that such a powerful clue about what light is?

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