Waves where the motion of the medium is at right angles to the direction of the wave's propagation are called transverse waves.

Here's a breakdown:

* Transverse waves: The particles of the medium oscillate perpendicular (at right angles) to the direction the wave travels. Think of a wave on a string or ripples on a pond.

* Longitudinal waves: The particles of the medium oscillate parallel to the direction the wave travels. Sound waves are a classic example, where air molecules compress and expand in the same direction the sound wave travels.

Let me know if you'd like to learn more about transverse waves or have any other questions!