Recent content by Physics Enemy

Thank you RedBelly. :-)

Yes you're right, it was sloppy of me. :) Thanks, I'm happy with this. So therefore: 1/10^15 = Constant * (Variation in T) Variation in T = Some Number So it's not a %, just +/- this number. Correct?

Sorry - The k is just a constant I put in, it's actually various quantities bundled together. So the dimensions do turn out to be correct. I just wanted to simplify and focus on the Q. This is the key point and thanks for your answer. Could you perhaps expand on this? At the moment it just...

I think he wants you to justify why they behave like particles in a gas, before you write down the equations. Perhaps Wiki it? I think you need to explain the assumptions. Hey, would you mind checking my thread? It's a basic numeracy one lol.

But isn't the idea that they are behaving like particles in a gas?

Isn't it something like: Assume the stars move about with a mean thermal energy, which is their KE. So KE = 1/2mv^2 = (3/2)KT Then mv^2 = 3kT => T = mv^2/3k?

Hi, Basically the question is about doppler shift. The formula is: (f2 - f1)/f1 = -kT ; f1 = Freq in object rest frame, f2 = Freq in lab frame The Q: Often, frequencies are compared to 1 part in 10^15. In order to make use of this level of accuracy, to what extent can T fluctuate? I...

I gave you the details. It's a conceptual Q about whether an electron can absorb a photon. Apparently it violates conservation laws. The second bit is about a centrifuge 'overcoming' this issue. Nothing else is needed.

dEdT = h/2Pi dE = (6.63 x 10^-34)/(2Pi * 10^-8) J dE = [(6.63 x 10^-34)/(2Pi * 10^-8 * 1.6 x10^-19)] eV dE = 6.6 x 10^-8 eV dE = 7 x 10^-8 eV (1 Sig Fig) The energy of the first excited state is 13.6/4 = 3.4 eV, so its energy uncertainty is tiny compared in comparison.

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elelin.html Hope that helps!

Hey, It seems like this is impossible because momentum conservation is violated. I had a Q where an electron underwent an energy transition and emitted a photon, and then they asked whether it was possible for the photon to be reabsorbed by the electron to undergo the same transition as...

Yes you're right. V x B = (V_y * B)xhat - (V_x * B)yhat + (0)zhat So the x component is B*ydot, and y component is -B*xdot

I actually disagree with their answer, shouldn't it be -y dot? x cross z gives -y, I think ...

Thanks, I realized a few mins ago lol. The x and z cross to give the y-direction. For some reason I also thought V was potential, not velocity. It's a little v, of course. :redface:

Basically the question is about a penning ion trap. You need to use the equation for the Lorentz Force, which I have. It says the trap electrodes have a potential: V(x,y,z) = A(2z^2 - x^2 - y^2); There's a superimposed uniform B-Field B = B(z hat) It then asks you to write down an...