Relations Of Refractive - Index

Description:

When a ray of light travels from optically denser medium to optically rarer medium it bends away from the normal and when a ray of light travels from optically rarer medium to optically denser medium it bends towards the normal.

If μ > 1, refracted ray bends towards normal.

If μ < 1, refracted ray bends away from the normal.

Principle of reversibility of light

If, after undergoing several reflections and refractions, the direction of ray of light is reversed, the ray traces its original path in the reverse direction.

By the principle of reversibility of light, if the direction of light in medium 2 is reversed then the ray retraces the path.

From figure, we can observe that −

And

Where,

μ₁₂ = Refractive index of medium 1 with respect to medium 2.

μ₂₁ = Refractive index of medium 2 with respect to medium 1.

Relation between refractive index when light is through 3 mediums

Let us consider a ray of light which travels through 3 mediums - medium 1, medium 2, medium 3 and then back to medium 1.

From figure, we can observe that −

By multiplying all the above equations, we get −

We know,

Where,

μ₃₂ = Refractive index of medium 3 with respect to medium 2.

μ₃₁ = Refractive index of medium 3 with respect to medium 1.

μ₂₁ = Refractive index of medium 2 with respect to medium 1.