Question

If light travels a distance x in t1 seconds in air and 5x distance in t2 seconds in a medium, then the refractive index of medium is

Answer 1

Velocity of light in air be v1 .

$\rm \: v1 = \dfrac{x}{t1}$

Velocity of light in medium be v2:

$\rm \: v2 = \dfrac{5x}{t2}$

Now, refractive index of medium w.r.t air

$\rm \mu = \dfrac{v1}{v2}$

$\rm \implies\mu = \dfrac{x/t1}{5x/t2}$

$\rm \implies\mu = \dfrac{t2}{5(t1)}$

So, Option 4) is correct !!!