Select the correct statement about refractive index from among the following.
1
Refractive index and reflection are the same phenomenon.
2
The ratio of the speed of light in vacuum to its speed in a specific medium is called the refractive index
3
The ratio of the speed of light in a specific medium to the speed of light in vacuum is called the refractive index.
4
Refractive index is the sum of the angle of incidence and the angle of refraction.