The frequency of a wave is determined by the formula:
\[
f = \frac{1}{T}
\]
Where \(f\) is the frequency and \(T\) is the time period. From the graph, we can observe that the time period is the length of one complete cycle, which is the distance between two consecutive peaks.
Looking at the graph, the time period \(T\) is 0.5 seconds.
Thus, the frequency is:
\[
f = \frac{1}{0.5} = 2 \, \text{Hz}
\]
Therefore, the frequency of the wave is 2 Hz.