Recent content by bojibridge

Ah, yes, of course! Thank you! I'd lose my head if it wasn't attached...

Homework Statement A hydrogen atom is placed in a uniform electric field E(t) given by E(t) = Enaught*exp(-a*t) (where a is a constant) for t >0. The atom is initially in the ground state. What is the probability that, as t→∞ , the atom makes a transition to the 2p state? I know...

Okay - can you expand on your last sentence? I'm not sure I totally understand what you're saying. (My mechanics is pretty rusty, sorry.) Oh, I just read your second post. I'm going to see if I can find it.

I'm not familiar with the term "variational indicator." Do you mean when you set the Lagrangian equal to... um, where you set it to some generalized external force?

Would the Lagrangian change if the spring's motion was damped? If so, how would you take that into account?

I'm curious as to how you would write a Lagrangian for a torsion pendulum. Say you've got some disc that has mass and it's attached by a spring with spring constant k to a stationary "ceiling" of some kind and has gravity acting on it downwards. So, not only has it got rotational energy, but...

Homework Statement You want to count all the galaxies out to a certain distance R(naught). If the universe were not expanding, then N (number of galaxies) would be proportional to R^3. Justify/derive. For an expanding universe, take into account the finite time that light takes to reach...

Homework Statement The photosphere of the universe corresponding to the age of decoupling of matter from radiation is presently 1.4 x 10^10 pc away from us. Calculate how far away a point on the photosphere was when the background radiation we see today was emitted. Also, dark matter...