Question

Light travels from air into glass of refractive index 1.5 what is the time taken by the light to travel through a piece of glass of 50 cm thickness

Answer 1

Here is the answer attached in the pic below. Hope it helps you. Cheers

Answer 2

Given: refractive index of glass = 1.5

The thickness of the glass = 50cm = 0.5 m

To Find: Time taken by the light to travel through a piece of glass

Solution:

The speed of light in air is 3 x 10⁸ m/s²

We know that the refractive index is the ratio of the speed of light in air to the speed of light in a medium

Refractive index of glass(u) = speed of light in air/speed of light in the glass(v)

1.5 = 3 x 10⁸ / v

v = 3 x 10⁸ / 1.5

v = 2 x 10⁸

Speed = $\frac{DISTANCE}{TIME}$

2 x 10⁸ = $\frac{0.5}{TIME}$

Time = 0.25 x 10⁻⁸s

        = 2.5 x 10⁻⁹ s

Therefore, the time in which the ray of light will cross a glass slab of 50cm is 2.5 x 10⁻⁹ s.