Answer:

Explanation:
In this case we will use the Bohr Atomic model.
We have that: 
We can calculate the centripetal force using the coulomb formula that states:

Where K=
and r is the distance.
Now we can say:

The mass of the electron is =
Kg
The charge magnitud of an electron and proton are= 
Substituting what we have:
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so:

The frequency f is related to the wavelength

by the equation

where v is the speed of the wave in the rope.
We can see from the formula that, if v is kept constant, smaller frequency means larger wavelength. So, the rope with frequency 2 Hz will have the longest wavelength.
Answer is in the question :)