The spectrum of an overhead fluorescent bulb reflected off a metal ring as viewed through a diffraction grating with 750 lines/mm is shown here. This image was obtained by taping the diffraction grating over the lens of a smartphone camera and pointing the camera directly at the ring from a slight angle (if you want to reproduce this image, don’t stand directly over the ring, as it will block the light from the fluorescent bulb). If you simply wish to view the effect, place the grating near your eye and stand over the ring at an angle that allows the overhead light to still shine down on the ring.
This would make an interesting demonstration in an astronomy or physics class. It shows that slitless spectroscopy preserves the shape of the object; this effect is sometimes seen in astronomy courses for planetary nebulae.1 The five strongest emission lines of...
