If a longitudinal wave is created in a medium that extends horizontally from left to right, then the particles of the medium will vibrate in what direction.

Question

anonymous · Answer

The particles will oscillate perpendicular to the wave's direction of travel.  So if the wave is traveling left to right, the particles will vibrate up and down, side to side, or somewhere in between.

anonymous · Answer

Transverse vibration is for transverse waves.
Longitudinal waves, like sound, have the vibration longitudinally, here, left-right-left-right.