2-1 Sound waves
Planar waves are waves with planar wavefronts
A ray is a directed line perpendicular to the wavefronts and indicates the direction of travel of the wavefronts.
emits sound waves equally in all directions.
A wavefront is an imaginary surface over which the displacements of particles are the same.
The wavefronts of
Away from the point source, we can approximate the wavefronts as planes.