Question

A ray of light is incident normally on a glass slab of thickness 5 cm and refractive index 1.6. The time taken to travel by a from source of slab is same as to travel through glass slab. The distance of source from the surface is ______.

Options

• 4 cm

• 8 cm

• 12 cm

• 16 cm

Answer 1

A ray of light is incident normally on a glass slab of thickness 5 cm and refractive index 1.6. The time taken to travel by a from source of slab is same as to travel through glass slab. The distance of source from the surface is 8 cm.

Explanation:

According to question,

Let 'x' denote the distance between the source and the glass slab's surface.

Time taken for light to travel from its source to the glass slab's surface (t₁) equals Time taken for light to travel inside the glass slab (t₂).

t₁ = `x/(3xx10^8)` and t₂ = `5/((3xx10^8)/1.6)`

[∵ Velocity of light in glass medium, = `"C"/"M"`]

∴ `x/(3xx10^8)=5/((3xx10^8)/1.6)`

or, x = 5 × 1.6 = 8.0 cm