# Laws of Refraction of light class 10 | cbse24

The phenomenon of refraction of light obeys the following two laws.

1:First law :-The incident ray, the refracted ray and the normal to the interface at the point of incident all lie in the some plane.

Example:-AO(incident ray ) OB(Refracted ray) and normal NN' all lie in the same plane(which is the plane of the paper)

2:Second law:
The ratio of sin of the angle of incidence and the sin of the angle of refraction is constant for a given pair of media.

$\frac{sini}{sinr}=1\mu _{2}=constant=\frac{\mu_{2}}{\mu _{1}}$

Where μ is refractive index of second medium with respect of first medium

### $Refrective-index(\mu )=\frac{Speed.of.light. in. vacuume}{Speed .of.light.in.medium}=\tfrac{c}{v}$

Refractive index of a medium with respect to vacuum is also called absolute refractive index

$1\mu _{2}=\frac{v_{1}}{v_{2}}=\frac{speed.of.light.in.medium1}{speed.of.light.in.medium2}=\frac{\frac{c}{\mu _{1}}}{\frac{c}{\mu _{2}}}=\frac{\mu _{2}}{\mu _{1}}$

### Factor on which the refractive index of a medium depends

1:Nature of the medium

2:Wavelength of the medium

3:Temperature

4:Nature of the surrounding medium

Note:
• $1\mu _{2}=\frac{v_{1}}{v_{2}}$   mean refractive index of medium 2 with respect to medium 1
• $2\mu _{1}=\frac{v_{2}}{v_{1}}$  mean refractive index of medium 1 with respect to medium2
• A substance having higher refractive index is optically denser than another substance having lower refractive index.μ↑ than density ↑
• $1\mu _{2}=\frac{1}{2\mu _{1}}$

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