What is Quantum mechaincs: Definition and 109 Discussions

No Wikipedia entry exists for this tag
  1. E

    Approaching the problem o 1D well that changes size

    Homework Statement You have a potential well, it's 1-dimensional and has a width of 0 to a. All of a sudden the wall of the well is pushed inward so that it's half as wide. Now the well is only extending from 0 to a/2. in the well is a particle (mass m) that is in the first excited state...
  2. E

    A (relatively) simple QM Problem, but seeking my mistake

    Homework Statement Find <r> and <r2> for an electron in the ground state of hydrogen. Express in terms of Bohr radius. Homework Equations We know the relevant wave functions are: R_{10} = \frac{c_0}{a}e^{r/a}Y^0_0 and Y^0_0 = \frac{1}{\sqrt{4\pi}} The Attempt at a Solution As I...
  3. T

    A good quntum mechanics book to review before grad school

    Hi , I finished my undergrad major in physics this fall. I wish to apply to grad school for next fall, so I need some book review books on physics, I n my university we followed Griffith's intro to QM as textbook, I solved almost all the problems there upto chapt 7, but this seemed a more...
  4. 2

    Help with deriving the Casimir Effect?

    I am at the very last part of a relatively long derivation of the Casimir effect, and I just don't understand the final step D: So far, I have derived the ground state energy to be \langle 0| \hat{H} |0\rangle = \delta (0) \int _{-\infty}^{\infty} dp \frac{1}{2} E And for a massless field...
  5. 2

    Question about creation and annihilation operators?

    Hello! I am reading about the creation and annihilation operators and I don't get how you find the creation operator from the annihilation one. The creation one is \hat{a}=\sqrt{\frac{m \omega}{2 \hbar}}\left( \hat{x}+\frac{i \hat{p}}{m \omega}\right) and the annihilation operator is...
  6. 2

    Trouble with Hermitian operators?

    I am looking at the derivation of the Heisenberg Uncertainty Principle presented here: http://socrates.berkeley.edu/~jemoore/p137a/uncertaintynotes.pdf and am confused about line (21)... I do not understand why AB and BA are complex conjugates of each other... (I'm still in high school so I...
  7. W

    Full Basis of Angular Momentum Eigenstates

    Homework Statement Consider the case of an atom with two unpaired electrons, both of which are in s-orbitals. Write the full basis of angular momentum eigenstates representing the coupled and uncoupled representations Homework Equations l=r×p lx=ypz-zpy ly=zpx-xpz lz=xpy-ypx l+=lx+ily...
  8. A

    Solution to the Schrödinger equation for a non rigid step

    I've been having troubles resolving the Schödinger's time independent one-dimensional equation when you have a particle that goes from a zone with a constant potential to a zone with another constant potential, yet the potential is a continuos function of the form: $$ V(x)=\left\{...
  9. Z

    How Do You Determine the Ground State Energy in a Spherical Infinite Well?

    Homework Statement A particle of mass ##m## is constrained to move between two concentric hard spheres of radii ##r = a## and ##r = b##. There is no potential between the spheres. Find the ground state energy and wave function. Homework Equations $$\frac{-\hbar^2}{2m} \frac{d^2 u}{dr^2} +...
Back
Top