wht is locus??wht a wave front actually is?
Any collection of points is known as a locus. A wave front is a locus of points oscillating in the same phase. For eg, if u throw a stone in water, circular ripples are generated, at an instant, all the points in the travelling are in the same phase and form a locus. This is known as a circular wave front. If you go very far away from the source, we will find that the ripple will ALMOST become striaght, this will give rise to a plane wave front.