Question

In which mesium speed of light is lesser glass or air .
Pls give a direct answer.
Glass or air.

Answer 1

Glass..................

Answer 2

The simplest picture is that light always travels at the speed of light. But in a material it travels at the speed of light until it hits an atom. It is then absorbed and re-emitted in the same direction, which takes a small amount of time.
The more this happens, the slower the effective average speed.
The denser the material, the more atoms there are in the way.
That is why light travels faster in air