What exactly do light-sensitive elements react to? Answered
I had an old (about 1970s) large power transistor (I think it was a field-effect one, but I am not completely sure...). Knowing it is supposed to be light-sensitive I took the top of the case off, and it has a small EMF between the collector and emitter when exposed to light. But the EMF from directly under electroluminescent lamps in the school corridor is about 10 times smaller than from lying on a sun-lit windowsill. So light-intensity can't be the only thing the EMF depends on... But what is the other thing?
PS It can't be UV, because well... we have glass in the windows at school, although it risks to get broken, as there is a football cup at the moment.