The speed of light in glass slab is ________ compared to that in air. Fill in the gap.
The refractive index of a medium is defined as n=cv, where c is the speed of light in the air and v is the speed of light in the medium.
The refractive index of the glass slab is n=1.5, which is greater than 1. Therefore, c>v or v<c.
Thus the speed of light in the glass slab is less as compared to the speed of light in the air.