Are umbrellas parabolas? Answered
I am trying to make a homemade spotlight and I need a parabolic reflector. Instead of sketching one out on my own (which I'm only semi-confident I can do correctly), I thought it might be possible to use an umbrella coated with tin foil as a reflector. I remember reading that they were parabolic somewhere, but I can't remember where I read it. Are they parabolas?