A wave front is an imaginary surface where;

Question

Question

Answer 1

CONCEPT:

F2 P.Y 23.5.20 Pallavi D 5

Wavefront: The locus of all particles in a medium, vibrating in the same phase is called waveFront.
The direction of propagation of light (ray of light) is perpendicular to the waveFront.
Every point on the given wavefront acts as a source of a new disturbance called secondary wavelets which travel in all directions with the velocity of light in the medium.
A surface touching these secondary wavelets tangentially in the forward direction at any instant gives the new wavefront at that instant. This is called a secondary wavefront.

EXPLANATION:

From above it is clear that, a wavefront is an imaginary surface where all particles lying on this vibrate in the same phase. Therefore option 1 is correct.