$$ $$ $$ $$ $$ $$ $$ $$ $$ $\text{Extra close brace or missing open brace}$ $\text{Extra close brace or missing open brace}$ $$

Finding Wavelength

You can measure the wavelength from the snapshot graph: it is the distance between two successive crests, troughs, or other matching parts on the wave. Alternatively, you can count the number of cycles $N$ that occur during a certain distance $d$, and then $\lambda =d/N$.

If you are given a history graph and the wavespeed, you can measure the >waves/period period from the history graph, and then use the formula $v=\frac{\lambda }{T}$.