Is there black light?

Answer

Not strictly speaking. ‘White’ light stands for a source that simultaneously emits light in all the colors we see, ‘black’ stands for a source that does not do that, that does not emit any colour. So we don’t see something that is black: if we do notice it, it is because it contrasts with the sources around it that we can see.

But of course that also has to do with ourselves. ‘Light’ is a form of (electromagnetic) radiation, but we only call ‘light’ that radiation that we can observe with our eyes, and that is only a part of the whole. What we do not see we call ‘black’, but that does not mean that it is not there, but rather that we cannot perceive it with our eyes. In that sense ‘black light’ does exist, it is the ‘light’ that we cannot see with our eyes.