Single Slit Diffraction

If coherent light went through a single slit would we get an interference pattern? The answer is yes, but how is this possible when we only have one source? Surely interference is the result of light from a number of sources arriving at the same place at the same time.

laser light passes through a single slit to produce this pattern.	laser light through a circular aperture ( a small hole ) produces this pattern.	Christiaan Huygens	A single slit as many point sources

We can explain this using Huygens' Theorem

We can think of a single slit, of width b, as actually being made up of very many point sources. These point sources interfere with each other to produce the single slit diffraction pattern.

Above is a graph of intensity against angle for single slit diffraction. To calculate the angle for the first minimum we use the equations above.