A transverse wave traveling from right to left will cause the medium to vibrate perpendicular to the direction of wave propagation.

Here's why:

* Transverse waves are defined by the fact that the particles of the medium move perpendicularly to the direction the wave travels.

* Right to left refers to the direction the wave itself is moving.

Therefore, if the wave is moving right to left, the medium will vibrate up and down (or side to side) as the wave passes through it.