Cross section Definition and 315 Threads

What is the cross section of a photon traversing the observable universe? That of a neutrino? Dark matter in general?

Calculating Surface area/volume from 2D cross section?? I'm feeling a little stupid today and I need some help...:-p Assume that I have a radially-symmetric 3D object (for example a candle stick or the base of a table lamp) and that I can calculate the surface area of the largest longitudinal...

What is "momentum transfer cross section" ? Hi all, I'm reading a book on electron-molecule interactions and I'm puzzled by a quantity (well, by the difference in definition of two quantities). The book is, for your information, "fundamental electron interactions with plasma processing gases"...

I got the first part of this question but can't seem to get the 2nd part.. A 105 V potential difference is applied to a space heater that dissipates 1000 W during operation. (a) What is its resistance during operation? 11.025 OHM (b) At what rate do electrons flow through any...

I have read about "Thompson Cross section for free electrons" My problem is there must be the other cross sections photons are scattered by free electrons. photons must be scattered by aka protons and as well by alpha particles. Is there any defined cross sctions for the other particles as...

In the book "Gauge Theories of the strong, weak, and electromagnetic interactions" by Chris Quigg the calculus of the scattering of proton-electron is esbosed (chapter 7, section 3 , pag 168). He get the result (in the lab frame): \frac{\mbox d^2\sigma}{\mbox d E^\prime\mbox...

Does anybody know where to get the expected cross section for Z at the LHC (pp at 14 TeV)? (it would be great if you could provide a reference).

In this problem, you will estimate the cross section for an earth-asteroid collision. In all that follows, assume that the Earth is fixed in space and that the radius of the asteroid is much less than the radius R of the earth. The mass of the Earth is M_e, and the mass of the asteroid is m. Use...

I'm going through my intro to mechanical engineering material and there was one thing I was never clear on: If you have a cross section of a rod, why isn't its' area at a cross section pi * r^2 as a opposed to piD^2/4, where D is the diameter?

Is anyone familiar with Breit-Wigner Cross section? Say, for a reaction with 2 particles in the initial state, 1 intermediate and 2 final: \sigma = \frac{g \pi \lambda^2 \Gamma_i \Gamma_f}{(E-E_0)^2 + \frac{\Gamma^2}{4}} I can't see why for the wavelength we should use the momentum of...

I'm looking either for online resources or reference to a good book. I've been trying to help someone with a homework problem in a course entitled, Elements of Mechanical Design which uses Mechanical Design of Machine Elements and Machines by Jack A. Collins. The book sucks. The system...

What is the differential cross section for photo-electric effect? Is there a paper that explains this in more detail? Thanks in advance for any responses!

Area moment of inertia--circular cross section From the bending beam calculation, the moment of inertia of the cross section with regard to a coplanor axis of rotation is used. If we have a circular "beam", the area moment of inertia of a circular disk of radius a about a diameter is I_d =...

Can someone explain what absorption cross section is and how it's figured into an equation? And what is irradiation?

If the area enclosed by an ellipse 4x^2+y^2=1 and its cross section is perpendicular to the x-axis then its volume is? I don't have the slightest clue how to do this? Maybe solve for 2y^2=1-4x^2 set the integral equal to pi times the intergral of 1/4 to 1 of 1-4x^2?