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NCERT Refraction of Light Science Chapter Class 10

:The phenomenon of bending of light ray which is travels obliquely from one transparent medium to another medium is call refraction of light.

Laws of Refraction:

The incident ray ,refracted ray and the normal to the interface of two media at the point of incidene , all lie on the same plane.

The ratio of sin of angle of incidence to the sin of angle of refraction for a given pair of media and a given color of light.

Sin i /sin r = constant ¹μ₂

¹μ₂ is a constant and known as refractive index of Medium 2 w.r.t Medium 1

Refractive Index:

Relative Refractive Index:

The refractive index of Medium 2 w.r.t refractive index of Medium1 is defined as the ratio of speed of light in medium 1 to the speed of light in medium 2.

¹μ₂ = speed of light in medium 1 / speed of light in medium 2.

¹μ₂ = v1/v2

¹μ₂ x ²μ₁ = (v1/v2) x (v2/v1 )=1

Absolute Refractive Index:

It is defined as the ratio of speed of light in air or vaccum to the speed of light on given medium.

Question: Find the refractive index of the following?

1. Glass = 2 x 10⁸
2. Water = 2.25 x 10⁸
3. Diamond = 1.25 x 10⁸

Answer:

1. μ_g = 3 x 10⁸ / 2 x 10⁸ = 1.5
2. μ_w =3 x 10⁸ / 2.25 x 10⁸ = 1.33
3. μ_d =3 x 10⁸ / 1.25 x 10⁸ = 2.4

¹μ₂=v1/v2

=c/v2 x v1/c

= c/v2 x 1/c/v1

= μ₂/μ₁

¹μ₂ =μ₂/μ₁

¹μ₂ x ²μ₁

= v1/v2 x v2/v1 = 1

¹μ₂ x ²μ₁ = 1