31. What is refractive index ? A.It is defined as the ratio of speed of light in the medium to the speed of light in vacuum. B.It is defined as the product of speed of light in medium and in vacuum. C.It is defined as the ratio of speed of light in vacuum to the speed of light in the medium. D.None of above
Option C Solution: The ratio of the velocity of light in a vacuum to its velocity in a specified medium.
