Waves have many uses in daily life.Radio, television transmission ,mobile communication ,remote control systems and heat energy radiation, are all applications of waves.These waves have their nature as either transverse or longitudinal .In transverse waves ,the vibration of particles is at right angles to the direction of wave travel e.g water waves ,waves on a string and all electromagnetic waves.In longitudinal waves ,the vibration of the particles is in a direction parallel to the direction of the wave travel e.g sound waves.

When vibration of particles is in a direction  along to the direction of the wave travel,what name is given to this nature of a wave?