Question:How do I calculate the wavelength of a wave from a graph?
First of all remind yourself that the wavelength is the distance for the wave to go through one complete vibration. So if you look at the diagram, the three most common places to measure the wavelength are shown.
NB. You can measure the wavelength starting at any position on a wave. By starting at one point and moving forward to the exactly equivalent point.
Notice that line 1 crosses the wave at point B - this is because the first point A is when the wave is falling, the same point on the graph occurs when the wave is falling again at C. The most common mistake students make is to thing that one wavelength will be a distance from A to B, when actually it must be A to C.