BACKGROUND INFORMATION:
Youngs experiment involved sunlight being allowed to pass through a pinhole, S and then at a considerable distance away , through pinholes S1 and S2. The two sets of spherical waves emerging from the two holes interfered with each otherinsuch a way as to form a symmetrical pattern of varying intensity on the screen AC. This experiment is shown below
The mathematical formula that was derived from this experiment is Λ = (a * y)/D, which can be re- arranged so that the seperation of the two slits is the subject of the equation,