Light passes from air to another medium

Light passes from air to another medium at point A. How long does it take the light ray to travel from A to B?

Using the geometry we can find refraction angle Θ.
$refraction angle$
$refraction angle$
$refraction angle$

Using Snell’s law we can find index of refraction of the medium

By assuming index of refraction on air is one (n₁ = 1).

$index of refraction$
$index of refraction$

n₂ = 1.9917

Index of refraction of the medium is 1.9917

Using above result we can find speed of light ray inside the medium
$index of refraction using velocities of two medium$

C = speed of light (Approximately 3 x 10⁸ m/s)

Speed of light ray inside the medium is 1.506 x 10⁸ m/s

Using geometry we can find distance AB

Distance from point A to B is 6.5 meters.

Using the distance and velocity inside the medium we can find the time taken to light ray to travel from point A to B.

Velocity = Distance / Time

Time = Distance / Velocity

Time = 6.5 m / 1.506 x 10⁸ m/s

Time = 4.316 x 10^-8 s

Time to light ray to travel from point A to B is 4.316 x 10^-8 seconds.