In this exhibit, half of the florescent tube is clear, while the other half is
coated with white phosphor. When you look at the different parts of the tube with a spectroscope, the clear end shows specific spectral colors. The coated end has these colors plus an additional continuous spectrum of colors due to the phosphors. The mercury gas in a fluorescent tube produces strong ultraviolet light, which the phosphor coating absorbs and re-emits in the continuous spectrum. It is this process which is called fluorescence.