What is the velocity of all electromagnetic waves in a vacuum?

Explanation:

All electromagnetic waves travel in a vacuum at the same speed, regardless of their frequency. The magnitude of their velocity is

This value is one of the universal constant and it is called speed of light.

According to Einstein's theory of special relativity, the value of c is the same for all inertial frames (it means that we measure always the same value of c in a vacuum, even if we are moving with respect to the light).

However, the speed of the electromagnetic waves decreases as they move through a medium. In particular, their speed decreases according to the equation:

where n is called index of refraction of the medium.

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none, its a machine