# Translations:Sinusoidal waves/32/en

Let us now concentrate on some spatial point. The pulses produced by the generator move toward this point, and they pass the point with the same frequency as the one at which they leave the source. The frequency of the wave motion is therefore also 100 Hz, and the time between passages of successive pulses is also 0.01 s. Furthermore, as the waves move, the spatial distance between any two adjacent pulses is always the same and is the wavelength ${\displaystyle \lambda }$. Because the pulses are separated by a distance ${\displaystyle \lambda }$ and because each pulse moves over this distance in a time T, it follows that the velocity of propagation is ${\displaystyle v{\rm {=}}\lambda /T}$. Using the relation ${\displaystyle f{\rm {=}}1/T}$, we again find that ${\displaystyle v{\rm {=}}f\lambda }$ or that the velocity of propagation of a periodic wave is the product of the frequency and the wavelength. This is an important relationship; in particular, it holds for sinusoidal waves.