Recent content by Chen

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    Can the Definite Integral of sinc(x) Be Solved Using Fourier Techniques?

    I'm studying a course in Fourier. In a multi-choice question, one of the answers asks for the value of the definite integral of sin(ax)/x over [-pi,pi]. I am wondering if there is a way to calculate this integral (I guess using Fourier techniques) or not. It is possible that it can't be solved...
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    High School Drop of water in slow motion - explanation needed

    Please see here: http://www.youtube.com/watch?v=n5bsQ_YDYCI&feature=player_embedded# First - wow. Second - I'm not sure I understand the mathematician's explanation. Why would there be a thin layer of air to begin with? Is this correct? Is there a different explanation for this...
    • Chen
    • Thread
    • Drop Explanation Motion Water
    • Replies: 2
    • Forum: Mechanics
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    Graduate Relation between decay rate (lifetime) and spectral width

    If I knew what I wanted to hear I wouldn't need to ask you for it. Can you please give others a chance to answer my question as well? I thank you for your answer but I want to hear other possible answers.
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    Graduate Relation between decay rate (lifetime) and spectral width

    Ok. Maybe someone else can provide a different explanation.
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    Graduate Relation between decay rate (lifetime) and spectral width

    Thanks, although that's not derived from Fermi's golden rule is it... I was hoping for a more intuitive explanation. Pressure broadening stems from enhanced stimulated emission, doppler broadening is obvious... where does the natural linewidth comes from?
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    Graduate Relation between decay rate (lifetime) and spectral width

    Well, doesn't it give the wrong result for the lineshape (sinc and not Lorentzian)?
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    Graduate Relation between decay rate (lifetime) and spectral width

    Hi, I am trying to understand exactly how and why the lifetime, or decay rate, of an atomic level determines the spectral width of the transition to this level. Also I would like to understand why the natural lineshape is a Lorentzian. I am familiar with the vague explanations involving...
    • Chen
    • Thread
    • Decay Decay rate Lifetime Rate Relation Width
    • Replies: 15
    • Forum: Quantum Physics
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    Magnetic field of a finite-length wire

    Thanks. But I know how to calculate this with Biot-Savart's law. I want to know where the application of Ampere's law to this problem fails.
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    Magnetic field of a finite-length wire

    There is a formula here: http://www.ac.wwu.edu/~vawter/PhysicsNet/Topics/MagneticField/MFStraitWire.html If we limit our discussion only to the center of the wire, theta=phi and you obtain the result of an infinite wire, times cos(theta). And I am not at all sure where in Ampere's law this...
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    Magnetic field of a finite-length wire

    Let's say I want to calculate the magnetic field at a distance d from the center of a wire of finite length L, carrying a current I. Why would it be wrong to apply Ampere's law to a circular path of radius d centered on the wire, and say that the integral of B.dl is simply B times 2pi*d...
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    Graduate Recursive solution of determinants

    Yes that would be correct, a bad case of dullness. Thanks.
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    Graduate Recursive solution of determinants

    After a bit of search I see that the method to solve this kind of recurrence relations is to assume a solution of the form A \lambda_1^N + B \lambda_2^N and find A and B from the initial conditions. However this is not exactly the form of the solution here... how come?
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    Graduate Complex conjugate an independent variable?

    Hmm, pardon my ignorance, but what does that wedge stand for? Thank you
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    Graduate Recursive solution of determinants

    Hi, I'm reading a paper where the determinant of the following matrix is solved for using some kind of recurisve method. The matrix is given by M_{ij} = A \delta_{i,j} - B \delta_{i,j-1} - C \delta_{i,j+1}, with i,j = 1...N and are NOT cyclic. The author sets D_N =...
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    Graduate Complex conjugate an independent variable?

    To give a concrete example to my last question, take a look here, at the second identity: http://www.pact.cpes.sussex.ac.uk/~markh/Teaching/RQF3/node22.html (this is actually exactly what I'm dealing with)