Here's another experiment that is extremely straightforward and simple. We know that thermo noise has no theoretical upper crest limit. Normally we refer to noise in terms of root mean square. When studying real thermo noise we see that given enough time the noise will eventually drift to a higher crest. The experiment is simple. Connect one resistor in series with an LED. That is it. To save yourself a lot of time you should pick a high frequency LED as used in GHz optics. This will provide a lot of bandwidth, which is what you want given voltage thermo noise is (4 K T R B)^0.5, where B = Bandwidth. Also you want to pick a resistor that matches the LED for an optimum effect. Also it doesn't hurt if the resistor is a noisy one such as carbon composite and as small as possible. Smaller carbon composite resistors generate more noise. Of course the *extra* noise is 1/f. This results in a resistor with real noise. When then voltage noise crest overcomes the LED's forward voltage then the LED will emit photon(s). Also note the LED emits photons far below the forward voltage. So in that sense, it is possible the LED will emit an occasional photon even when the noise voltage is far below the LED's forward voltage.
Now the question is, "Where do we aim the photons?" Note the above experiment is in an isolated system. We have two experiments. Experiment #1, the resistor absorbs the photons. Experiment #2, the LED absorbs its own photons (we coat the LED with opaque material). The main difference between the two experiments is the resistor in experiment #2 is colder than the resistor in experiment #1. Note, the above experiments could require vast amounts of time, depending on the exact parts used in such experiments. Given enough time, the noise crest will reach the LED's forward voltage. For those who are less patient, it is possible you will see some photons emitted even below the LED's forward voltage. Regards, Paul Lowrance ____________________________________________________________________________________ Sponsored Link Online degrees - find the right program to advance your career. Www.nextag.com
