You know how light works, right? The energy of an electromagnetic wave dictates wavelength, and there's only a very small amount of electromagnetic energy that we can actually see. Then there's infrared, microwaves, radio waves, gamma rays... all that crap.
The thing is, even if you can't see it, that isn't to say you can't receive it. Let's just say there are frequencies of energy that scientists don't know too much about. That isn't to say they haven't studied it. It's just that anybody who actually sees it, and mind you, it isn't hard to reproduce if you know just where it is, goes a little, well... fucking nuts. I can't be too specific, that'd be stupid. But it's between 10,000,000,000,000,000,000Hz and 10,000,000,000,000,000,000,000Hz. Odds are pretty good it'll fry your optic nerve once you see it. But that's sorta for the best.
See, the optic nerve leads to your brain in a pretty sensitive spot. Right next to the Oblongata and Thalamas. These control most of your very primitive functions... breathing, heart beat, desire to eat, desire to kill.
Point is, it's a good thing they -usually- go blind. It makes you mad. People start ripping, tearing, thrashing at whoever is around them. If nobody is around them, they even tear themselves to shreds, not recognizing their limbs for their own when their flailing hands happen upon another part of their body.
Like I said, though, it's not too common for somebody to see this kinda radiation. But still... There's a reason nobody is allowed near the two cities around Chernobyl. And a damn good reason the disaster at Three Mile Island was kept so low key.