I was reading my latest Reader's Digest in which appears an article about ultraviolet photography. The article explains that this kind of photography utilises a technique known as ultraviolet induced visible fluorescence. The article says that the technique allows flowers to reveal spectacular colours "you'd expect on another planet". I thought that rather unlikely as presumably if we can see them they are simply different arrangements of colours we see everyday. So I did a little digging and found that the colours are a result of fluorescence, something I've not ever really thought about before. The situation is that these flowers absorb the UV wavelengths and then emit light in longer (and therefore visible) wavelengths. So far so good. But here's where I need a little clarification. I assume that these emissions are always occurring in typical sunlight - that is fluorescent materials must be both reflecting and emitting visible wavelengths (as everyday sunlight contains light across the spectrum from UV to IR). I assume that we do not usually "see" emitted wavelengths as they are presumably of less intensity than the reflected wavelengths and hence our cones are "swamped" by the reflected wavelengths? Similarly, does it also follow that fluorescence doesn't depend on a particular set of wavelengths? That is, presumably fluorescent materials can absorb visible wavelengths and emit visible longer wavelengths (or even IR wavelengths)? Perhaps it is quite commonplace in nature? Does that mean then that the everyday world of colour is really a mix of both reflected and emitted wavelengths in some or many cases?