Mam plzz, derive snell's law without using huygens principle.
There are at least three ways of deriving this law of refraction, or how light bends when it travels from one material to another. The easiest method is indicated in the two pictures below. The light is traveling ^ to the wave crests, and when it enters the lower material and slows down, it still must travel ^ to the crests. The sketch on the right is a magnification of the one on the left. It shows two triangles with a common hypotenuse H. Play around with this and show that (1/v1)sinq 1 = (1/v2)sinq 2, Then multiply both sides by the speed of light in a vacuum, c, and define n = c/v, so
n1sinq 1=n2sinq 2.
Hope this helps.