What accounts for the acceleration or deceleration of light when it travels from one medium to another?

“When light passes through different mediums speed changes but who provide acceleration to change velocity?” This question was posted by Jishnu Answer: Just imagine you are participating in a cross country race. When the road is good you can travel faster; but if the path is a marshy place, your speed will decrease. This is ...Read the full post

Why the ray of light passing through optical center of a lens passes undeviated while when it passes through other points on the interface of the lens, it gets refracted?

Deviation is the change in direction of the ray while passing through the lens. The middle portion of the lens is comparatively flat and there is a point on the principal axis and inside the sphere read more