Hi Yash!

Huygens’ Principle:

Every point on a wavefront acts as a source of secondary wavelets that spread out in all directions with the speed of light in that medium. The new wavefront at any later time is the common tangent (envelope) to all these secondary wavelets.

Using Huygens’ principle to derive the laws of refraction:

When a plane wavefront travels from one medium to another, the speed of light changes. Suppose light goes from a rarer medium (speed = $v_1$) to a denser medium (speed = $v_2$).

From the wave construction:

$\dfrac{\sin i}{\sin r} = \dfrac{v_1}{v_2}$

But we know refractive index $n = \dfrac{c}{v}$

So, $\dfrac{\sin i}{\sin r} = \dfrac{n_2}{n_1}$

Or

$n_1 \sin i = n_2 \sin r$

This is Snell’s Law of Refraction.

Thus, the laws of refraction are:

The incident ray, refracted ray, and the normal at the point of incidence lie in the same plane.

$n_1 \sin i = n_2 \sin r$

Hope it helps!