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  1. DrClaude

    Collection of Science Jokes P2

    http://smbc-comics.com/comic/duuude
  2. DrClaude

    I Photon Absorption

    By Kirchhoff's law, it won't emit much in the visible range in any case.
  3. DrClaude

    Is there an alternate fuel that de-emphasizes carbon?

    Why not add non-toxic and non-polluting, while you're at it. If there was such a chemical, you can be sure someone would be getting fifty rich right now by producing it. And why shy away from carbon compounds? The problem wrt climate change is fossil fuels. If you could make fuel using...
  4. DrClaude

    I Unexplained phenomena

    What I mean is that you have to justify this statement: What are things for which scientists didn't even bother to explain?
  5. DrClaude

    I Unexplained phenomena

    I don't think this statement is correct.
  6. DrClaude

    Complex representation of a wave

    You missed an i in the exponential. https://en.wikipedia.org/wiki/Euler%27s_formula I'm not sure that this answers your question, but as you wrote, to general solution is a sum of a sine and a cosine. There can be combined into a phase-shifted cosine or sine. By convention, most of the time...
  7. DrClaude

    Two-level quantum system (from Sakurai)

    Once you have the eigenvalues, you put them back in the eigenequation and solve for the coefficients of the eigenvectors ##(c_1, c_2)^T##. Note that the solution is not unique, so you can either solve simultaneously the normalization equation ##|c_1|^2 + |c_2|^2 = 1## or take arbitrarily ##c_1...
  8. DrClaude

    How to calculate a wave function in time t

    Sorry, I hadn't paid attention to the particular wave function you were working with. (There is a typo in what you wrote: it should be ##d^2/dx^2##.) I was answering the second part of As for the first part, there is a typo in the answer. Norm is conserved and the normalization factor remains...
  9. DrClaude

    How to calculate a wave function in time t

    This is incorrect. The actual equation (for a time-independent Hamiltonian) is $$\psi \left ( x, t \right ) = e^{-i \hat{H} t/\hbar} \psi \left ( x,0 \right )$$ It is only in the case where the exponential of the operator is acting on an eigenstate of that operator that you can replace the...
  10. DrClaude

    Why do I keep finding more new rocks in my garden year after year?

    That's the "Brazil nut effect," or granular convection. See in particular https://en.wikipedia.org/wiki/Granular_convection#Geology
  11. DrClaude

    You have to post your question in the Introductory Physics Homework Help Forum.

    You have to post your question in the Introductory Physics Homework Help Forum.
  12. DrClaude

    Go to the proper forum: for questions related to a specific exercise/problem, go to the...

    Go to the proper forum: for questions related to a specific exercise/problem, go to the appropriate Homework Help forum (e.g., Introductory Physics Homework Help). For more general questions, find the forum that covers the subfield of physics or another science (e.g., Classical Physics). In the...
  13. DrClaude

    Mathematica Elliptic function

    The problem is that the second argument in JacobiSN and JacobiDN is ##m##, not ##k## (##k = \sqrt{m}##). See https://www.johndcook.com/blog/2018/10/12/jacobi-function-nomenclature/
  14. DrClaude

    Tube television reception

    It is whatever electromagnetic noise there is at the frequency of the channel. That noise will vary from channel to channel and from one location to another.
  15. DrClaude

    I Numerical ODE Fail

    Also, please post your code as text, since that allows others to copy-and-paste it.
  16. DrClaude

    I Numerical ODE Fail

    Check what happens to the numerical solution when you start at ##t=10## with the exact value as a starting point.
  17. DrClaude

    A Conceptual doubt in a problem on Wien's Law

    You should be able to answer the question without knowing the melting point of the material being heated. That's it. If the iron is just starting to glow at 700 nm, then the peak wavelength must still be in the infra-red, so T < 4140 K.
  18. DrClaude

    Mathematica Elliptic function

    Yes, that oscillates between 1 and 2 (Mathematica 12.0.0.0).
  19. DrClaude

    MATLAB No damping but the solution to simple harmonic oscillator damps?

    What are the initial conditions? For "fun," I implemented the Duffing oscillator in C using RKF45 from GSL, which should be the same integrator as the one used by Matlab, and I get the correct solution for the undamped case.
  20. DrClaude

    I Schrodinger equation for a free particle in 3d space

    To add to what @Nugatory said, ##a \in \mathbb{C}## is a constant and ##x## is the independent variable, as in the differentiation.
  21. DrClaude

    Collection of Lame Jokes

    The tyranny of "common sense." Things are often more complicated than most people think.
  22. DrClaude

    Fermi Temperature and Black-body radiation

    That's incorrect. The Fermi temperature is simply the conversion of the Fermi energy to units of temperature, with the Fermi energy based on the T = 0 distribution of fermions (degenerate Fermi gas). It is not the temperature at which the "lowest energy state" is attained. The usefulness of...
  23. DrClaude

    Applying BCS-BEC Crossover

    Thanks for sharing!
  24. DrClaude

    Kinetic Energy and Radiant Energy levels

    For an isolated atom/molecule, there is no way to couple the internal and external degrees of freedom. In other words, there is no mechanism that would convert kinetic energy to, e.g., electronic or vibrational energy. Therefore, it is not possible to make atoms "glow" by accelerating them...
  25. DrClaude

    A Bose-Einstein condensate

    How many grands of sand do you need to make a pile? Condensates can easily be made with 106-107 atoms.
  26. DrClaude

    A Conceptual doubt in a problem on Wien's Law

    I'll explain later, after @warhammer has had time to work the problem. I think you have to think about all that is happening, not just plug-and-play with the equation.
  27. DrClaude

    I Question about the quantum harmonic oscillator

    The trick is to embed BB codes such that $$ is not interpreted as the equation delimiter. In this example, I put color tags around the second $ (choosing black, so the effect is invisible).
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