A plane wavefront propagating from a rarer into a denser medium is incident at an angle of incidence i on a refracting surface. Draw a diagram showing incident wavefront and refracted wavefront . Hence verify Snell's laws of refraction.

Explanation

Here `v_(1) and v_(2)` are speeds of light in medium 1 and 2 as shown BC= vt to get the shape of wave front draw an arc of radius `v_(2)t` form A towards medium 2.
If CE is tangent plane then `AE=v_(2) t,`
CE represents refracted wave front
In `triangle ABC and triangle AEC sin i= (BC)/(AC)=(v_(1)t)/(AC) , sin r = (AE)/(AC) = (v_(2)t)/(AC)`
So `(sin i)/(sin r)= (v_(1)t)/(cancel (AC))xx (cancel(AC))/(v_(2)t)=v_(1)/v_(2)`
If c is speed of light in vaccum then
`n_(1)=c/v_(1) and n_(2)= c/v_(2)" " rArr v_(1) =c/n_(1)and v_(2) =c/n_(2)`
where `n_(1) and n_(2)` refractive indices of medium 1 and 2
`(sin i) /(sin r)=(c//n_(1))/(c//n_(2)) = n_(2)/n_(1) rArr" "n_(1) sin i= n_(2) sin r`
`rArr` Snell's law