A Light Source Sends out Waves in all the Directions
In a homogeneous medium, the velocity of light waves is same everywhere. So the disturbances reach all such particles at the same time. These particles are at the same distance from the source and so they vibrate in phase with each other. The locus of all such particles is called wave front.
The shapes of different wavefronts are :Spherical, cylindrical, plane and so on.
Point source-p of a spherical wave front
You must have noticed that in all the above diagrams the arrows representing the ray of light are perpendicular to the wavefront.
