Answer:
They have a frequency of 2 hertz
Explanation:
Frequency is the number of occurrences of a repeating event per unit of time and Wavelength is the distance from one crest to another, or from one trough to another.
In the question, it is stated that the leaf does two full up and down bobs, this means that it completes 2 full cycles in one second. Therefore, its frequency is 2/s
where, s⁻¹ is hertz
so, They have a frequency of 2 hertz