# Recent content by Garlic

1. ### Landau levels: Hamiltonian with ladder operators

Dear PF, I hope I've formulated my question understandable enough. Thank you for your time, Garli
2. ### I Spin evolution over time

Thank you for your quick replies :) I have found a link where it says that the associated time evolution unitary operator $U(t,0)$ is similar to the operator $R_n(α)$ which rotates a vector by an angle α around the axis defined by the vector $\bar{n}$. I diddn't understand how a...
3. ### I Spin evolution over time

Dear PF, As an excercise I am to find out how the expectation value of the spin operator evolves over time. There was a hint, stating that it is enough to show that  e^{i \frac{\phi ( \hat{n} \cdot \sigma )}{2}} \sigma_i e^{- i \frac{\phi ( \hat{n} \cdot \sigma )}{2}} = [R_{ \hat{n} }]_{ij}...
4. ### I Question about the quantum harmonic oscillator

Thank you for your replies :) As I previewed my equations, they diddn't appear as Latex formulas, so I thought I got the syntax wrong and gave up :) So today I've looked at the MIT text for a few hours and tried to understand every step of it. It was certainly very interesting. I am surprised...
5. ### I Question about the quantum harmonic oscillator

Dear PF community, I am back with a question :) The solutions for the quantum harmonic oscillator can be found by solving the Schrödinger's equation with: Hψ = -hbar/2m d²/dx² ψ + ½mω²x² ψ = Eψ Solving the differential equation with ψ=C exp(-αx²/2) gives: -hbar/2m (-α + α²x²)ψ + ½mω²x²ψ = Eψ...
6. ### Which pH Meter to buy

I mean in our laboratory classes for second semester physics major students, it is something unusual that someone uses a pH Meter. He told that the pH Meter that litup suggested is being sold already calibrated, so I wouldn't have to calibrate it before using it, but once something happens it is...
7. ### Which pH Meter to buy

So, after asking my professor, he told me that it is really unusual that someone uses pH-meters in the laboratory, and that it is better to use indicator papers instead, as we are unexperienced with the calibration. Anyways thank you for your answers
8. ### Which pH Meter to buy

Like I said, this is for basic inorganic chemistry laboratory experiments that I'm going to have in our university in a few weeks. The pH-Meter doesn't have to have high resolution, but it needs to be reliable. With my experiment partners we have decided that it would be okay to spend a little...
9. ### Which pH Meter to buy

Thanks for your quick reply. I think I can just ask my professor for calibration liquid instead of buying it in bulk size. And I'm wondering, why can't I use any cheap liquid whose pH value I know (eg pure water)? Do you think it is necessary that I buy pH indicator papers even if I have the pH...
10. ### Which pH Meter to buy

Hello everyone, In a few weeks I am going to have my anorganic chemistry laboratory experiments, and I want to buy one PH-Meter. I'm looking for a model that is realible but not expensive (in the order of 20-40 bucks) I'll be happy to hear your suggestions Thanks :smile:
11. ### Problem with a derivative

Thank you! :smile:
12. ### Problem with a derivative

Okay, so it appears, that I haven't correctly derived the function at the beginning, so the problem begins with the first row.
13. ### Problem with a derivative

Hello PF, 1. Homework Statement I've been having problems with the deriative of a function, although I thought I've done everything right, my solution doesn't match with the right solution. I have no clue what (or if) I've done anything wrong, or simply don't know the tricks I was supposed to...
14. ### Problem on a question about the gravitation potential

Oh, now I understand it.. :smile: Thank you
15. ### Problem on a question about the gravitation potential

Hello everyone 1. Homework Statement In the solution of a question, regarding the gravitational force fields and gravitational potential when the mass is inside earth (where the height of the mass is lower than the radius of earth), the step where we take the integral of the force in order to...