Answer:
λ = L / # _ periods
Explanation:
We don't have the image of the string, but a wavelength is the minimum distance when the wave repeats, therefore the distance between two consecutive maxima is the wavelength in the string
A method used to decrease the error is to measure the distance in several consecutive maxima and divide the number of them, in this way the error in the measurements is divided between all the points, so the value of the wavelength is more exact
λ = L / # _ periods
