Here's a visual representation:

```

/\ /\ /\

/ \ / \ / \

/____\ /____\ /____\

^ ^ ^

| | |

λ λ λ

```

In this diagram:

* The wavy lines represent the wave.

* The arrows point to two consecutive crests.

* The symbol 'λ' (lambda) represents the wavelength.

So, to find the wavelength on a wave diagram, simply measure the distance between any two identical points on the wave, such as two crests or two troughs.