What is a periodic transverse wave?
It is a wave that has a period (that is it repeats at regular intervals) and the wave effect is perpendicular (transverse) to the direction of propagation. Examples: A wave in a shallow tank of water (ripple tank) created by a regularly oscillating thing dipped into the water. It is transverse because the wave motion at some point is up and down while the wave travels along the surface of the water. Electromagnetic waves (like radio waves) are periodic transverse waves because the electric and magnetic fields that make the wave are perpendicular to the direction that the wave travels.
