Diffraction Patterns and Polarization in Physics

Diffraction is interference that light does to itself. Send a wavefront through a single opening and every part of that opening becomes a source, so the light arriving at the screen is the sum of countless contributions and the sum is not always bright. The result is a broad central band with fainter bands beside it, and the narrower the opening the wider the spread. Multiply the opening into thousands of parallel slits and the bands sharpen into lines fine enough to separate the colours of a star. Polarization is the other half of this topic, and there the question is not how much light arrives but which way it is vibrating, which a simple filter can answer. The blocks give the single-slit minima and intensity, the resolution limit of a telescope or an eye, the grating relations and the Bragg condition, then the two laws that describe a polarizer.