The standing wave in the figure has 4 nodes and 3 antinodes.
The wavelength of a standing wave is given by,
![\lambda=(2)/(n)L](https://img.qammunity.org/2023/formulas/physics/high-school/ifow56r4jipy15nungn5fdlxfct1sobmw1.png)
Where n=number of nodes-1
From the figure n=3
Therefore the wavelength is,
![\lambda=(2)/(3)L](https://img.qammunity.org/2023/formulas/physics/high-school/b0d7bi7kkt4tfqz3jcq707yxztivhuw572.png)
Therefore the wavelength of the stationary wave produced in the given string of length L is (2/3)L.