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According to Snell's law :

$${n_1 \over n_2} = {v_2 \over v_1}$$

$v_2 = v_1 n_1 / n_2$

Assuming that $n_1$ is vacuum , we will find the following equation:

$$v = c / n$$

(We may find the same equation directly according to the definition of refractive index : $v = c /n$)

Theoretically , according to this equation in a certain medium the speed of light can become small and even 0.

1- Under these conditions , will the light will be at rest ?

2- If true , a viewer in such medium can move faster than the speed of light. Theoretically, is such occasion possible ? Under certain conditions , is it possible to move faster than the light?

Michael
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1 Answers1

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Light will never be completely at rest, but we have succeeded in slowing it down significantly. (See this for example)

In a medium, particles can move faster than the speed of light. (The speed of light in that medium)
In fact, this is used in some particle accelerators to detect certain particles.
When a charged particle travels faster than the speed of light in a medium, it emits Cherenkov Radiation. (See this for a brief explanation)

Omry
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