Question

Derive Snell’s law of refraction using Huygens’s wave theory.

Answer 1

AB - Incident wavefront

A'B' - Refracted wavefront

i = ∠CAN = ∠BAA'

r = ∠NA'a' = ∠AA'B'

`therefore  "sin i"/"sin r" = "BA′"/"AB′"`

BA' = V₁ t ; AB = V₂t

`therefore "sin i"/"sin r" = ("V"_1)/("V"_2)`

`("V"_1)/("V"_2)` is called refractive index, it's constant for two particular optical medium.

∴ `"sin i"/"sin r" = "constant"`