Spherical Wave Fronts
We know, the locus of the particles in a wave having the same phase is the wave front. The wave fronts near the source of light are spherical. In the figure, A, B and C etc are spherical wavefronts. The following definition of the spherical wave front can be given-
If the locus of the particles in a wave is spherical then the wave front is called the spherical wave front. The wave having spherical wave front is called a spherical wave.
Fig: Spherical wave fronts
On this wave surface, every particle observed will have the same energy and will be oscillating at the same phase because these particles before time t (i.e., before traveling the distance ct), had received the energy from the source together at the same time. When the light waves propagate through a medium at any instant of time all the wave are in a single plane They are called wavefront and when a point source is placed then it will be spherical and when the source is at infinite then it will be plane like sunrays and when source is a line then it will be cylindrical.
