Why are blacklights used to show proteins and bacteria? Is it related to their ability to make white colors glow? Don't black lights just radiate in the ultraviolet/purple range?
As you well know, our eyes can only see the visible spectrum (lets say from red to violet). Now, if you turn on a black light in a dark room you can only see a purplish glow. You are "blind" to the ultraviolet light that the bulb is also producing. The things you see under a black light (when illuminating a fluorescent poster, a brand new white t-shirt, etc) are called phosphors. The phosphors is a substance that absorbs the UV light and emits it as visible light. The same general principle holds with bacteria and proteins. Some bacteria contains plasmind, which in turn contains a certain gene, which codes for the Green Flourescent Protein. So you can put the plasmid in the bacteria, the plasmid starts making that protein in the bacteria and the result is a glowing pile of goo. (try a google search on the matter, there are tons of articles, etc. )