Recent content by DiracRules

Hello! I'm an undergraduate in physics engineering student who's thinking about his future. I would like to work in the field of quantum cryptography or communication with light, or -more or less- to do the same kind of research as Anton Zeilinger. Which kind of MSc and PhD should I take and...

\frac{x^2}{a^2}+\frac{y^2}{b^2}=1 The distance r of every point of the ellipses from the centre of the frame of reference is always between min(a,b)\leq r\leq max(a,b). By definition, the major axis is defined as max(a,b) while the minor axis is min(a,b).

Wow, I didn't consider this aspect! Thank you for pointing this out! I'm studying these things right now. Well, I think that you are right, the plane of incidence loses its meaning. THOUGH, the thing here maybe another one - I say maybe because I've been thinking of it for 10 minutes, but as it...

That's correct. Remember that \sum \vec{F}=m\vec{a}

Did you looked at cosmic rays? They are made up mainly from highly energetic protons (90%) and gamma rays, and the interesting thing is that when they hit the atmosphere, they produce a shower of exotic particles that can help theoretical physicists a lot. In fact, the energies of that radiation...

You can face this problem at least in two ways: 1) Calculate explicitly the force with the Coulomb expression \vec{F}=\frac{q_1q_2}{4\pi\epsilon r^2} 2) Solve the problem "geometrically": how do you build a charged plane with a hole? You can think either...

I edited my previous post, get a glance at it. The thing is, you don't need any theorem. The way to solve this limit is the first thing you should have studied, that is: trying substituting the value and see what happens.

no, with substitution I mean simply to put the value x=pi/2 in the limits. \lim_{x\rightarrow\frac{\pi}{2}}\frac{x^2-\frac{\pi^2}{4}}{\tan(x)^2}=\frac{x^2-\frac{\pi^2}{4}}{\tan(x)^2}|_{x=\frac{\pi}{2}}=\frac{0^{\pm}}{+\infty}=0^{\pm} This is the way to solve this limit...

Electron/Positron Impact & Photon Energies BTW, can you help me with another thing? "An electron and a positron are moving against each other. at the point of impact both have the velocity 0.6c Two gamma photons are sent out. What is each of theirs energy?" Well, the sum of momentum...

Did you draw the graph? That could be helpful. Anyway, look at the equation you wrote: K=h\nu-\phi=h\nu-h\nu_f What's the relationship between the frequency \nu and the energy?

There is no reason to evaluate this limit using a theorem. You can solve it by "substitution", and the form you get is not indeterminate.

Isn't that a row vector? ||V||=\sqrt{V*\cdot V}, where V* is the complex conjugate and the dot is the inner product.

You are missing that \frac{0}{\infty} is not a form of indetermination: \frac{0}{\infty}=0

Yep |\vec{v}_{t=3}|=\sqrt{\left[\left.\frac{dx}{dt}\right|_{t=3}\right]^2+\left[\left.\frac{dy}{dt}\right|_{t=3}\right]^2}

What is the magnitude of the vector \vec{v}=[v_x,v_y]? Or, how do you evaluate the magnitude of a vector knowing its components? And, \vec{v}=[v_x,v_y]=[\frac{dx}{dt},\frac{dy}{dt}]