State the laws of refraction of light.

#### Solution 1

There are two laws of refraction:-

**First law of refraction:-**

The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant. This is known as Snell’s law. Mathematically, it can be expressed as:

`sini/sin r=n_12`

Here, n_{12} is the relative refractive index of medium 1 with respect to medium 2.

**Second law of refraction:-**

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

If a light ray goes from medium 1 to medium 2, then the refractive index of medium 1 with respect to medium 2 is expressed as:

`n_12="Speed of light in medium 2"/"Speed of light in medium 1"=v_2/v_1`

Here, v_{1} and v_{2} are the speeds of light in medium 1 and medium 2, respectively.

#### Solution 2

**The laws of refraction are as follows:**

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

(ii) The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for the given color of light and for the given pair of media.