The type of wave where particles in the medium experience up and down forces perpendicular to the direction of wave propagation is a transverse wave.

Here's why:

* Transverse waves: The oscillations of the medium particles are perpendicular to the direction the wave travels. Imagine a rope tied to a wall. If you shake the rope up and down, the wave travels horizontally along the rope, but the rope itself moves vertically.

* Longitudinal waves: The oscillations of the medium particles are parallel to the direction the wave travels. Think of a spring. If you push one end of the spring, the compressions and rarefactions (areas of compression and expansion) travel along the spring, and the spring itself moves back and forth in the same direction as the wave.

Examples of Transverse Waves:

* Light waves

* Electromagnetic waves

* Waves on a string

* Water waves (although water waves are more complex and have both transverse and longitudinal components)