Video Encyclopedia :The commercial Crookes' tube with a paddlewheel.

Video Encyclopedia :Crush wintergreen lifesavers and they give off faint flashes of light.

A sinusoidal wave is printed on transparent material that can be wound up. As the radius of the windings gets bigger the waves add constructively (line up) or destructively (not lined up) like the De Broglie wavelengths in the Bohr orbit of the hydrogen atom.

Two diffraction gratings are oriented at right angles and a small lecture laser projects a pattern of dots similar to x-ray diffraction.