Question

the wave front due to a point source at a finite distance from the source is

Answer 1

first of all , understand what is wavefront ?

wavefront : Each point source of light is a centre of disturbance from which waves spread in all directions. The locus of all the particles of the medium vibrating in the same phase at a given instant is called a wavefront.

you should know that, wave front due to a point source at a finite distance from the source is spherical as shown in figure.

and the wavefront due to a point source at a infinite distance from the source is plane as shown in figure.

hence, answer is " plane wavefront ".

Answer 2

' wavefront 'which is basically the particular point created by light . It is the definite point from which the rays are coming out from that particular point .

In the case of an electromagnetic wave, the structure of wavefront is like a surface of identical phase . Also by conventional optics we can modify it . So at a finite source of distance the wavefront is spherical.