I know that when we see red light (via electromagnetic frequencies in the red range) and blue light (via electromagnetic frequencies in the blue range) at the same time, we perceive it as magenta light.
Is it possible for non visible electromagnetic frequencies (such as ultraviolet and infrared) to combine in a way that makes us see it as a visible light?
The short answer is no we cant. Notice that the magenta you see does not really exist on its own; it's our brain filling in the gaps and mixing impulses. As for combining UV and IR I am not an expert at this field and I would gladly appreciate some exceptions to the logic I'm about to put forward. This is because the cone cells/receptors in our eyes only respond to visible light. We can see magenta because the two cones are being activated together and our brain perceives this impulse as magenta. But neither UV nor Infra-red light would stimulate the cones at least in the visual sense. Hence, there are no signals for the brain to process into any color. Thus, it seems to be that we cant combine UV and Infra-red to form visible light, at least not by just photons of those two frequencies.
A useful answer to read and support the argument: Why does adding red light with blue light give purple light?
