The natural frequency of an object depends on its

composition, its size and shape.

Explanation:

All objects have a frequency that characterizes them, which is called natural frequency. This means that if a disturbance or vibration is emitted near the object, it will begin to vibrate due to its natural frequency.

It should be noted that there are objects that have more than one natural frequency, and this depends on the composition of the object, its elasticity, its shape and size.

positive reinforcement? ?

frequency or wavelenth of em radiation in a vacuum