Franck–Hertz Experiment
The now-famous Franck–Hertz experiment elegantly supported Niels Bohr’s model of the atom, with electrons orbiting the nucleus with specific, discrete energies. Franck and Hertz were awarded the Nobel Prize in Physics in 1925 for this work.
Our college science complex has some amazing stuff, and I always look for esoteric items to photograph.
This was a good one for my 7,777 photo posted to Flickr.