L1-32
Show what the inside of a laser looks like, and to show that the laser removes lots of spectral components from the light in the tube and only lets one wavelength out.
The metal cover has been removed from a weak helium-neon laser, allowing the internal components to be seen, including the tube and the mirrors. Using a hand-held diffraction grating the light from in the tube can be seen to have a large number of spectral components. The light outside hits a white screen; looking at the spot with the grating shows that it is monochromatic, illustrating the lasing action.