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For an electromagnetic wave travelling through vacuum, what is the ratio of the magnetic field amplitude to the electric field amplitude?

1. The speed of light in vacuum
2. The reciprocal of the speed of light in vacuum
3. The ratio of magnetic permeability to electric susceptibility of vacuum
4. 1

Correct answer: The reciprocal of the speed of light in vacuum

Solution

In vacuum E0 = c*B0, hence the ratio of magnetic-field amplitude to electric-field amplitude B0/E0 = 1/c, the reciprocal of the speed of light.

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