Question

If a ray of light passes from medium $I$ to medium $I$ without any change of direction, what can be said about the refractive indices of these media (angle $i$is not zero)?

Answer 1

To answer the question we need to have a clear concept about refractive index, reflected ray and refracted ray. As a light wave travels from $I$ to medium $I$, and proceeds in the same direction as a refracted ray, so it can create its own angle of refraction.

Complete step by step solution:
In optics a ray is indeed an idealised model of light, acquired by selecting a line which is perpendicular to wave fronts of an actual light, so this points in the way of energy flow.

The incident ray is a light ray that strikes the floor. The angle here between ray as well as the perpendicular or normal to the ground is the angle of incidence.

If a light wave travels from $I$ to medium $I$ and moves in the same direction as a refracted ray, the angle between the refracted ray and the usual line is its own angle of refraction, in which case the refractive indices of all mediums are the same, meaning that the light ray does not change its course from $I$ to medium $I$.

Note: The reflected ray referring to a defined incident ray, seems to be the ray that reflects the light reflected by the object. The angle here between regular surface and the reflecting ray is regarded as the angle of reflection.
The light that is emitted through the surface is the refracted ray or emitted ray referring to a given incident ray. The angle between such a ray and the normal is regarded as the angle of refraction, and this is defined by Snell's Law.