In the arrangement shown in the figure below, an object of mass m can be hung from a string (linear mass density $\mu$ = 2.00 g/m) that passes over a light (massless) pulley. The string is connected to a vibrator with constant frequency $f$, and the length of the string between point P and the pulley is $L = 2.00 m$. When the mass m of the object is either 16.0 kg or 25.0 kg, standing waves are observed in the string.
No standing waves are observed for any other mass between these values.
$n$ = number of nodes from 25kg
$n + 1$ = number of nodes from 16kg
I do not understand why they have only integer 1 difference between the numbers of nodes of 25 and 16kg...
Anybody know why they put n + 1 for 16kg? If we do that, the problems becomes easy to solve.