Recent content by CDL

Homework Statement Laser probes are being used to examine the states of atoms and molecules at high temporal resolution. A laser operating at a wavelength of 400 nm produces a 1 femtosecond pulse. Compute the mean frequency and frequency spread, ∆ν, of this laser pulse. Homework Equations c =...

Homework Statement I am reading through Griffiths' Electrodynamics, and I have come to the scenario in the Relativity chapter where in an inertial reference frame ##S##, we have a wire, with positive charges (linear density ##\lambda##) moving to the right at speed ##v##, and negative charges...

Yep, if we consistently orient the surface. Thanks! you have been a great help.

So here we are considering the volume bounded by the sphere and the cube, what comes in goes out, so the sphere and the three cube surfaces share the same flux? For example, could we also say that we know the flux through the whole sphere, and since the electric field due to the charge is...

Interesting problem, I shall give it a go when I get up to conductors : ~ )

Is this because we have ##\nabla \cdot \textbf{E} = \textbf{0}## everywhere but the point charge? When is this principle applicable? By direct computation using a surface integral? Cool!

An eighth? That would give ##\frac{q}{24 \epsilon_0}## :eek: Why can we think of the charge like this (shell theorem)? Why not some other shape? When applying Gauss' law, and a charge is on the boundary of a surface, do we usually think about charges this way?

Oh yes, sorry, the top face would have non-zero flux too, but this gets it down to ##\frac{q}{3\epsilon_0}## only.. The top, front and right faces have non-zero flux but isn't the ##\textbf{E}## field produced by the charge tangential to the bottom, back and left faces?

Homework Statement Griffiths' Introduction to Electrodynamics problem 2.10, Homework Equations Gauss' Law, ##\int_{S} \textbf{E}\cdot \textbf{dS} = \frac{Q_{\text{enc}}}{\epsilon_0}##[/B]The Attempt at a Solution It seems reasonable that the flux through the shaded surface and the front...

Homework Statement Suppose we have a regular n-gon with identical charges at each vertex. What force would a charge ##Q## at the centre feel? What would the force on the charge ##Q## be if one of the charges at the vertices were removed? [/B]Homework Equations Principle of Superposition, the...

I have just finished my first semester of third year undergraduate physics, and have a 3-4 week break before my next semester, in which I will be taking a third course in electromagnetism (classical electrodynamics). It is my second course with a full focus on electromagnetism, since in first...

Homework Statement Consider scattering of a particle of mass ##m## on the potential $$U(r) = \begin{cases} 0, & r \geq b\\ W, & r < b \\ \end{cases}$$ Where ##W## is some arbitrary chosen constant, and the radius ##b## is considered a small parameter. Find the cross section ##\sigma## in the...

I am reading Griffiths' Introduction to Quantum Mechanics, specifically the chapter on scattering. He is discussing the scenario where an incoming beam of particles scatter off an azimuthally symmetric target. At large separation ##r## from the scattering centre, the wavefunction for incoming...

Sorry! ##\frac{1}{\lambda} >>10^{-17} s## and so ##\lambda << 10^{17} Hz##. I made a mistake with the direction of the first inequality sign in my previous post. Thank you very much for your help.

I used the fact that ##\hbar## will be ##\frac{1}{e}## of the initial value ##\hbar_0## at ##t = \frac{1}{\lambda}##, and that ##\frac{\hbar_0}{13.6\text{eV}} \approx 10^{-17}## Hence, we can write ##\frac{1}{\lambda} << 10^{-17} \Leftrightarrow \lambda << 10^{17}## Does this arise from the...