The pictures show the waves emitted by two point sources in a ripple tank. The picture on the right shows the amplitude of the waves, and the one on the left shows the intensity.
The coordinates of the two sources are (-2, 0) and (+2, 0). For any point on the screen you can calculate the path length difference to that point by measuring its coordinates (hold down the left mouse button and read the coordinates in the yellow box), and entering the values in the boxes below. Click on "Calculate paths" and the results will appear below. The wavelength of these waves is 2 units. Pick a point where there is destructive/constructive interference; what is the relationship between the wavelength and the path length difference?