# 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?

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...
3. ### 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...
4. ### 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...
5. ### 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...
6. ### 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...
7. ### 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...
8. ### 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...
9. ### 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...
10. ### 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...
11. ### Question about doppler shift in relativity

I've got a somewhat simple question, and I think its from me overlooking something stupid...but how does using doppler shift work if in any moving rest frame the speed of light is supposed to stay at 3(10^8) m/s? I know that E=hc/λ, so for the wavelength of the light λ to change, the only thing...
12. ### Any ideas for unsolved topics in Mathematical Physics?

Homework Statement Not really sure where this question belongs, but it is based on a school assignment so I'll put it here. I'm a Physics major and math minor, and I am about halfway through my first group of advanced physics courses (namely intro classes for analytical mechanics, modern...
13. ### Wavelength for highest radiation per unit wavelength

Homework Statement At what wavelength does a cavity at 6000 degrees Kelvin radiate most per unit wavelength? Homework Equations $$\rho_T(\lambda)d\lambda=\frac{8\pi{hc}}{\lambda^5}\frac{d\lambda}{e^{{hc}/{\lambda{kT}}}-1}$$ The Attempt at a Solution I'm pretty new to this whole...
14. ### Problem using integral form of Work K.E. Thm

Homework Statement I have this problem where the earth immediately loses all orbital velocity and begins to fall towards the sun, and I need to find the time it takes for the earth to hit it. Seemed straight forward enough. Homework Equations Started with the work k.e. theorem...
15. ### RL circuit inductive reactance problem

Homework Statement There's a coil, resistance R=7Ω, and inductance L=1mH, and its powered by a generator with variable frequency and Vmax=10V. At what frequency is inductive reactance equal to resistance? (when z=R√2) Homework Equations z=R√2, z=√(R2+(ωL)2) The Attempt at a...
16. ### LC circuit, space between dielectric plates

Homework Statement If the max E-field in the capacitor is E=1.2(103) N/C and the space between the plates is filled with a dielectric of constant 100,000, what is the separation between the plates? Homework Equations I know C=kεoA/d where k is the dielectric constant, A is the area of...
17. ### Induced current with two solenoids

Homework Statement so theres two solenoids on the same axis of symmetry, and the smaller one inside the larger one has a resistance of 11 ohms, 1000 turns, and radius .02 meters. the outer solenoid has n 18000 turns per meter, and had a current that is increasing at a constant rate with...
18. ### Proof of vector circulation

Homework Statement So a, b, and c are points in the plane. Let nab, nbc, and nca be vectors perpendicular to ab(vector), bc(vector), and ca(vector) respectively, and point towards the exterior of the triangle abc. Also, |nab|=|ab(vector)|, |nbc|=|bc(vector)|, and |nca|=|ca(vector)|. Show...
19. ### Deflection of electron beam in cathode ray tube

Homework Statement Part a) Deflection of the electron beam in a cathode ray tube television set has electrons accelerated until they have K.E. of 25 keV. What is the magnetic field magnitude required to deflect the electron beam 3.3 cm when the magnetic field is 8 cm long? Part b) When...
20. ### Speed of a pendulum at lowest point

Homework Statement I am told to find the speed of a pendulum bob at the lowest point of the swing where the initial angle of displacement is θ=5.7° and the period of the pendulum is 2.5 seconds. Homework Equations K.E.=.5mv2, T=2∏√(L/g), P.E.=mgh, h=L-Lcosθ=L(1-cosθ) The Attempt at...
21. ### Changing order of integration double integral

Homework Statement Set up an integral for the ∫∫xydA for the region bounded by y=x, y=2x-2, and y=0. Set up the dxdy integral, then the dydx integral, then evaluate the simplest of the two. Homework Equations The Attempt at a Solution I drew the region which was easy enough, and...
22. ### Gaussian sphere problem

Homework Statement The problem states that you have a spherical shell with inner radius Ri=1 cm and outer radius R0=2 cm. The shell also has uniform charge density of ρ=10-3 N/m3. I found the first few answers of the question already. First was to get the charge of the shell, which is simply...
23. ### How would water vapor contamination affect PV=nRT

Homework Statement Doing a lab here, but were kind of stuck. This lab is meant to experiment the formula PV=nRT, and the set up is a canister of CO^2 with a fixed volume that has a pressure sensor connected to it reading in pascals. We heat up the CO^2 by placing the canister in a beaker of...
24. ### Ideal gas expansion problem

Homework Statement Okay so I'm trying to figure out how to get this answer. Theres a souffle made of some ingredients and filled with these ingredients along with some air. Everything starts off at 283.15 K and gets heated in the oven to 463.65 K. Also assume that the air expands with heat...
25. ### Coulombs law, initial speed to collide with other nucleus

Homework Statement A helium nucleus has radius rHe = 1.9 fm, mass m = 6.6 × 10-27 kg, and charge +2e. A gold nucleus has charge +87e and radius rAu = 7.0 fm. What initial speed must a helium nucleus have if it is to come into contact with a fixed gold nucleus in a head on collision...