Diffraction

The best way to look at diffraction of waves (and this works for any type of wave: water, sound, light, etc.) is to think of a wave front hitting a barrier with a small gap in the barrier. The wave front passes through the barrier and become dispersed as it moves away from the barrier.

We are going to look at three different types of diffraction: single-slit, circular, and double-slit diffraction.

Single-slit diffraction is when a wave front encounters a barrier with only a small vertical hole in it (longer than it is wide). If you were to measure the intensity of the wave on the other side of the barrier, you would get a pattern much like this:

The following pictures show how single-slit diffraction actually works.

Circular diffraction is diffraction through a circular aperture. This is important for resolution in telescopes.

Notice, that if you make d smaller, λ also gets smaller, therefore, you have better resolution.

Lastly, double-slit diffraction gives a shape similar to single-slit, but a tad different. In the case of double-slit diffraction, a wave front will encounter two slits separated by a small distance, s.