Answer: The correct answer is "the ratio of the speed of the light in a vacuum to the speed of light in the material through which it is passing".
Explanation:
The expression for the refractive index is as follows:
[tex]R.I= \frac{c}{v}[/tex]
Here, R.I is the refractive index, c is the velocity of the light in vacuum and v is the velocity of light in medium.
Refractive index: It is defined as the ratio of the velocity of light rays travelling in a vacuum to the velocity of light rays travelling in a specific medium or the ratio of the speed of the light in a vacuum to the speed of light in the material through which it is passing. It describes how the fast light travels through the material.
It is dimensionless quantity. It measures the bending of a light when it passes from one medium to another.
Therefore, the correct option is first statement from the given options.
