A wave that moves back and forth at right angles is called a transverse wave.

Here's why:

* Transverse means "across" or "perpendicular."

* In a transverse wave, the oscillations of the medium (or the disturbance) are perpendicular to the direction the wave travels.

Think of a rope tied to a post. If you shake the rope up and down, the wave you create travels along the rope, but the rope itself moves up and down (perpendicular to the direction of the wave).

Some common examples of transverse waves include:

* Light waves

* Electromagnetic waves

* Waves on a string

* Water waves (to some extent - they have a bit of longitudinal motion as well)