The velocity of light in a stationary medium is u =c/n where c is the velocity of light in vacuum and n is the refractive index of the material (see 63.1). Find the velocity of light in the medium moving at a constant speed relative to the source of light.

Answer

Hint. Consider the reference frame fixed to the medium which moves at a speed with respect to the source of light.

Explanation

Suppose a substance approaches the light source with a velocity v. Then, according to the formula for the addition of velocities, we obtain
`u.=(u+v)/(1+uv//c^(2))=(c//n|v)/(1+v//cn)`
If the substance moves away from the light source, then
`u.=(C//n-v)/(1-v//cn)`