On the basis of Huygen.s wave theory, prove Snell.s law of refraction of light. Draw a neat and labelled diagram. (Postulates of Huygen.s wave theory not required)

Explanation

Proof of Snell.s law of refraction by Huygen.s wave theory :
Let, speed of light in rarer medium be vi m/s and in denser medium, be `v_(2)` m/s.
So, `DD.=v_(1)t`
In the same time `BB.=v_(2)t`
In `DeltaBDD." "sini=(DD.)/(BD.)" "......(1)`
In `DeltaBB.D." "sinr=(BB.)/(BD.)" "......(2)`

Dividing equation (1) by equation (2), we get
`(sini)/(sinr)=((DD.)/(BD.))/((BB.)/(BD.))`
`(sini)/(sinr)=(DD.)/(BB.)`
`=(v_(1)t)/(v_(2)t)`
`(sini)/(sinr)=(v_(1))/(v_(2))=""_(1)mu_(2)`
i.e., `""_(1)mu_(2)=(sini)/(sinr)`
This is called Snell.s law of refraction. Hence, Snell.s law is verified .