Detectors Definition and 109 Threads

Hey, I'm new to these forums and am just learning about quantum physics. I was wondering about the detectors used to pick up on photons. How exactly do these detectors work? What about the ones described which detect a photon but allow it pass through? Also, if a detector were designed...

http://www.livescience.com/041129_lie_detection.html

Ive known about this story for awhile, but is there any truth to it?

Hi, I always fascinated by the idea of Medal Detector, they are everywhere. In Libraries, stores... What is the myth behind those machines?

I was reading something today about it being stupid to own a radar detector in Australia because the police carry radar detector detectors with them. Is this even possible? I would have assumed that radar detectors don't send out a signal of sorts but only attempt to detect incoming radar...

There's a square detector of area A. When a point source is placed at the center of this detector, half of the emitted particles are detected. What fraction of the particles are detected when the point source is placed a distance x away? I figured that at x=0, 50% of the particles are...

I just noticed my new $10 smoke detector contains a few microcuries or less of radioactive Americium. Anyone one knows how these work? Why this element? It's the first time I see an application for it.

What are basic principles of clinically used AIDS (from blood) detectors ?

How is it possible that TV detector's work like the ones used by the TV licensing vans, is it by measuring the TV broadcast signals power loss ?