# Search results

1. ### How to make thick line error bar for plot

Disclaimer: I'm not exactly sure that this topic would belong in this thread but I don't think it would fit better anywhere else. I'm working on writing a paper for my grad research project and my PI wants me to model the plots after another paper that our lab published in the past, but I'm...
2. ### Can total angular momentum j be negative?

I appreciate the response! Cheers
3. ### Can total angular momentum j be negative?

Homework Statement I'm just stuck on one part of a larger problem. I need to find the range of total angular momentum values for an electron in a j-j coupling scheme. Homework Equations j= l + and - 1/2 The Attempt at a Solution The electrons here are in a 5d 6s configuration. So for the...
4. ### Present for favorite professor

Not really sure if this topic belongs here...but anyways, I am getting my physics degree soon and I want to get my favorite physics professor a gift before I go off to grad school. She wrote me a letter of rec and I took 5 classes with her, so she definitely deserves it. She practically does...
5. ### Small question about atomic form factor calculation

Homework Statement This problem just has me find an atomic form factor for some arbitrary basis atom in a bravais lattice where the electron wave function is given (it has a dependence on the Bohr radius in an exponential). I calculated the form factor (a very long, nasty integral that...
6. ### Speed of light in unusual materials

Ah! Thank you! This is precisely the answer I was looking for. Much appreciated DrDu.
7. ### Speed of light in unusual materials

Just for a little background: What brought this up originally was that I have been working in a Quantum Optics lab as of late, and I am trying to reproduce part of a thesis experiment that a classmate just finished last semester. This thesis explored Plasmonic Resonant Solitons in Metallic...
8. ### Speed of light in unusual materials

This is my point exactly...I am aware of Brewster's angle, and it makes sense to me that to calculate the speed of light in anything translucent you would just need to find the speed of light in air experimentally and then from there you could employ Brewster's angle to find the index of...
9. ### Speed of light in unusual materials

Thanks Dave! That was really enlightening...I guess for a more thorough understanding I'll have to wait a month until I start my first Solid State Physics class. Question: Is the end of this FAQ saying that determining the speed of light in a given material (assuming the photons are outside...
10. ### Speed of light in unusual materials

Hi all, I've recently learned some details about refractive indices in different media that I never knew about before. Up until now, I was aware that the speed light travels in a certain medium is dependent on the wavelength of light used. However I wasn't aware that for different kinds of...
11. ### Is there a formula for this gaussian integral

Ahhh thank you thank you thank you! That works 100%! Man I've been trying to get this formula for a week...I really appreciate it.
12. ### Is there a formula for this gaussian integral

I'm sorry i just dont think that's correct. Try wolframalpha. I know the formulas for the x, x^2, x^3 cases, but not the x^4. But everything up to x^3 agrees with wolframalpha's output, and this formula you guys are giving doesnt look very similar and does not agree...
13. ### Is there a formula for this gaussian integral

Sorry, but you can't :/
14. ### Is there a formula for this gaussian integral

Is there a formula for this gaussian integral: $$int_{-\infty}^{\infty}{x^4}{e^{-a(x-b)^2}}dx$$ I've tried wikipedia and they only have formulas for the integrand with only x*e^... not x^4e^... Wolframalpha won't do it either, because I actually have an integral that looks just like that...
15. ### Potential well, harmonic oscillator

Homework Statement Parabolic harmonic oscillator potential well. A particle is trapped in the well, oscillating classically back and forth between x=b and x=-b. The potential jumps from Vo to zero at x=a and x=-a. The particle's energy is Vo/2. I need to find the potential function V(x) in...
16. ### Electron emits a photon that emits an electron

Oh okay i think i understand now. Thanks guys
17. ### Electron emits a photon that emits an electron

So im pretty sure that by compare it you mean the total energy of the electron is the difference between the energy required to kick it out and the total energy of the photon. However, i am still somewhat stuck on finding out how to get the kinetic energy out of this. If i use the total E of...
18. ### Electron emits a photon that emits an electron

What do i do with that energy required though?
19. ### Electron emits a photon that emits an electron

Would the energy required be E=-13.6 eV * 1^2 / 4^2?
20. ### Electron emits a photon that emits an electron

Homework Statement This problem has a photon that was emitted by an electron orbiting a hydrogen atom that dropped from n=5 orbit to n=2. I need to find out, if this photon emitted an electron from the n=4 orbit of another hydrogen atom, what the k.e. of this electron would be. Homework...
21. ### Rutherford scattering thin gold foil

Homework Statement The fraction of 6.0 MeV protons scattered by a thin gold foil, of density 19.3 g/cm^3, from the incident beam into a region where scattering angles exceed 60° is equal to 2.0(10^-5). Calculate the thickness of the gold foil. Homework Equations...
22. ### Proving a property of the dirac delta function

Ahhhhh wow okay that totally makes sense now. Thank you vela. I guess for some reason I was thinking that if you substituted something that way it would be like a change of variable but it actually isn't. I kept trying to use the definition...
23. ### Proving a property of the dirac delta function

Am I just making this harder than it needs to be or what? I honestly am really stuck here and I've been thinking about this problem since last night
24. ### Proving a property of the dirac delta function

Yes, I think its quite obvious i am aware of that since I used that fact when I integrated by parts...
25. ### Proving a property of the dirac delta function

Yeah but how does knowing that first definition help with that second integral? I don't see any way to use that to solve the second integral...
26. ### Proving a property of the dirac delta function

Thanks for the reply tiny tim. I see what you are saying about the first part of the formula I reached. However for the second part, if I applied the definition of the delta function I would have a very odd integral that I would really have no idea how to solve.
27. ### Proving a property of the dirac delta function

Homework Statement Prove this theorem regarding a property of the Dirac Delta Function: $$\int_{-\infty}^{\infty}f(x)\delta'(x-a)dx=-f'(a)$$ (by using integration by parts) Homework Equations We know that δ(x) can be defined as...
28. ### Question about doppler shift in relativity

Actually, I just found a page in my text containing the derivation for the Longitudinal Doppler Shift Formula of Relativity Theory. Pretty cool stuff. So apparently one photon will have a higher frequency than the "rest frequency", and the other will have a lower frequency than the "rest frequency".
29. ### Question about doppler shift in relativity

@phinds, I was actually trying to think of this problem by relating it to cosmological doppler shift, because I'm a little more familiar with that than doppler shift on a quantum scale...@DaleSpam I just recently started learning about four-vectors, yes.
30. ### Question about doppler shift in relativity

Okay so yeah I was overlooking something stupid haha. Well I'm just a little confused about this homework problem, its about pair annihilation. A positron-electron pair annihilate into two photons, and I need to find the speed an observer would have to move to observe one of the photons...