Answer: l = 0.1 m.
Explanation of the solution to the problem: to solve this problem, you must use the following formula:
l (st.) = l / 2, where l (st.) (lambda) is the length of the standing wave, l is the full wavelength, that is, the distance from the first to the third node.
A standing wave is a wave formed when two opposing traveling waves are superimposed.
The standing wavelength is the distance between two adjacent nodes (for example, between the first and second or the second and third). Therefore, to find the length of the standing wave, you need to divide the distance given in the problem statement by 2:
l (st.) = l / 2 = 0.2 / 2 = 0.1 m.
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