What is radiating or reflecting light called?

Answer 1

We might generally characterize something that radiates light energy as luminescent. There are different reasons materials or substances radiate light, and a term like bio-luminescentmight appear. There are organisms that generate light, like a firefly (to name one). The term radio-luminescent might refer to the something like the glow of radium, which was painted on aircraft instrument indicators so they could be seen in the dark. Radioactive decay is the source of the energy that creates the light in that case. There are "variations" like incandescent, which is the generation of light with thermal (heat) energy as its source. A "regular" light bulb does this (having converted electrical energy into thermal energy as a first step). The term fluorescent refers to the generation of light directly from the ionizing effects of electricity, and we know about fluorescent lights, too. We might also encounter a couple of other odd terms with "escent" at the end that speak to this property.