Recent content by arcnets

I think what you're basically talking about is the "spin-statistics-theorem". I think it says that fermions obey the Pauli principle, while bosons do not.

cesiumfrog, I understand that you see my error in my derivation of relativistic mass but not in the rest of the "proof". I admit there is a weak spot there. OK, how about this: (ct)^2 - x^2 = invariant. Let's define the 4-vector X = (ct; ix). Then the invariant is the square length of...

You are fast! Where do you see an error?

I think the answer is yes. Here's a derivation which I rather like. You start from the invariance of light speed: (ct)^2 - x^2 = invariant. Now you multiply by m and divide by t, getting (mc)^2 - (mv)^2 = invariant (since v = x/t). Now you look at two frames, one of which is the rest...

I think this is correct. What I meant by "the whole space" is actually the backwards lightcone of B.

I think it's more simple, but I can't do the nice formulae, sorry... First, from the invariance of c for all observers, you get the equation (ct)^2 - x^2 = invariant for all observers. Next, you multiply with m^2 and divide by t^2: (mc)^2 - (mx/t)^2 = invariant. Now if one observer (0) is...

I think Feynman wants to illustrate something called "Huyghens' Principle". Another way to illustrate this, is a hologram. A hologram can be cut in half, and each part still carries the whole picture. That's because a hologram is the record of a light wave, and the information in a wave is...

1 - I think we need the heat bath to keep temperature constant. This means that our system can exchange energy with the heat bath, but since input = output, the net change is zero. Same as with an isolated system. 2 - I think we don't care about the exact mechanism, but use conservation...

OK, the lesson is tomorrow, let's see what happens. Thanks a lot for your input ZapperZ. :smile:

I think I understand why you scratch your head. Maybe I make it more complicated than it is. Well. I did some classical calculation. First, I calculated the amplitude of the electric field produced by the light (.6 Watts over 1 cm^2). I came up with 24.000 V/m which is quite weak. In such a...

Yes, Ok. Sorry if I explained badly. My goal was to look at the photoelectric effect from a purely classical point of view, and make a classical prediction. A quantitative prediction *without* using photons. Then to show (in class) by experiment that this prediction is wrong. It must...

Yes, it is indeed. But I actually did this experiment. I had .6 Watts of light being absorbed by the cathode (caesium), so the upper limit for photocurrent is .3 Amperes, since an electron needs ~2 eV to escape. What I actually measured was 1.5 x 10^-7 Amperes of photocurrent. So the best part...

Yes OK, I know that. So the electrons start to oscillate because they're in an oscillating field. The stronger the light, the stronger the oscillations, OK. But oscillation doesn't mean they get out of the metal, does it?

Hiya, I'm about to teach the photoelectric effect in class. Everybody knows that observations contradict the classical prediction. Which is: Stopping voltage schould go up with light intensity. OK. But I have a problem: What EXACTLY is the classical prediction? I mean, is there a formula that...

OK, thank you. It seems to me that the most basic physical problem - two pointlike particles with e.m. interaction - can not be solved by Newtonian physics. Because we cannot calculate the forces. Or am I wrong...?