## Essential University Physics: Volume 1 (4th Edition)

We know the following equation: $\frac{2L}{v}=mT$ Since $T=\frac{1}{f}$, it follows: $\frac{2L}{v}=\frac{m}{f} \\ L = \frac{mv}{2f}$ Recall, $v=\lambda f$. Thus: $L = \frac{m\lambda f}{2f}=\frac{m \lambda}{2}$