btbdance

It appears as if the answer to my question has been lost from the conversation.... could you please give me pointers.

In the process called fluorescence, some substances absorb photons of one kind of radiation (e.g. ultraviolet radiation), and give out photons of a different kind (e.g. visible light). When infrared radiation falls on these materials, visible light is not emitted. Why not? (no further information about fluorescence to be included)