Camera problems ...

I have an iMac wt OS X El Capitain. Recently whenever I open Face Time, Photo Booth, or any program requiring the camera, it will operate fine for a couple of seconds, and the green camera light will go off. The camera will then periodically turn back on, but then quickly off again. It might be a hardware problem, or maybe something else. I've had problem after problem since purchasing my iMac, so IDK.