Define wavefront. Draw the shape of refracted wavefront when the plane incident wave undergoes refraction from optically denser medium to rarer medium. Hence prove Snell’s law of refraction.
Answer
A locus of points in space which oscillate in the same phase is called a wavefront .
That is, the phase difference between any two points of the same wavefront is zero .
Let us assume an incident wavefront AB incident on an interface between 2 media with refraction indices n1>n2.
According to Huygen’s wave theory:
- A source of light gives out waves in all directions.
- Every point on the wavefront is a source of disturbance. These disturbances called secondary wavelets, travel in all directions.
- The time taken by secondary wavelets to travel from primary to secondary wavefront is a constant .
Therefore, on the basis on these statements we can say that: