Question

1. what causes a disturbance that results in a wave?

Explanation:

In physics (a subfield of Natural Science), a wave is a disturbance that transfers energy. The cause of the disturbance leading to a wave is a vibration (or oscillation). For example, in a water wave, the disturbance can be caused by the vibration of a source like a stone being dropped (causing water particles to vibrate), or in a sound wave, the vibration of an object (like a tuning fork) causes air particles to vibrate, creating the wave. In electromagnetic waves, it's the oscillation of electric and magnetic fields. So the fundamental cause is a vibrating source that disturbs the medium (or space, in the case of EM waves) and transfers energy, resulting in a wave.

Answer:

A vibration (or oscillation) of a source (such as an object, field, etc.) that disturbs a medium (or space) and transfers energy, resulting in a wave.