The type of waves where the motion of particles is perpendicular to the direction the wave travels are transverse waves.

Here's a breakdown:

* Transverse waves: Imagine shaking a rope up and down. The wave travels horizontally along the rope, but the individual particles of the rope move up and down, perpendicular to the wave's direction.

* Longitudinal waves: In these waves, the particles move back and forth in the same direction as the wave travels. A good example is sound waves, where air molecules compress and expand in the same direction the sound is moving.

Let me know if you'd like more details on any type of wave!