Re: quick question
From: Old Man (nomail_at_nomail.net)
Date: 10/30/04
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Date: Sat, 30 Oct 2004 18:44:50 -0500
"Andr? Michaud" <srp@microtec.net> wrote in message news:562f286c.0410300602.701bc96a@posting.google.com...
> vreyes@sdsc.edu wrote in message news:<66c0b98b.0410281809.335b1aa4@posting.google.com>...
> > Hi there, I am a Ph.D. biologist whose physics knowledge is rusty.
> > I know that the equation for the energy of a wave is E=hv, so only
> > the frequency of a wave affects its energy. How about its amplitude?
> > My intuition tells me that the amplitude of a wave must in some way
> > affect its energy (in a direct way, presumably). Can a physics expert
> > give me an answer? Grateful biologist.
>
> I see that you got quite a variety of answers, but none seemed to
> the address your question, which was how to straightforwardly get
> to the amplitude associated to the energy of a photon.
>
> The amplitude of the energy of a photon is "connected" to its energy,
> but it does not "affect" it. To get a feel of the amplitude associated
> to the energy of a given photon, you only need to adapt the treatment
> of simple harmonic motion to the frequency of the photon.
>
> Take any frequency f you wish to find the amplitude of.
>
> Then calculate its angular velocity per second.
>
> w = 2 pi f
>
> w here represents the omega variable of simple harmonic motion.
> its value is in radians per second (rad/s)
> f is the frequency in Hz (Hertz)
>
> The velocity of all photons being the speed of light (c), you will
> of course use c for the velocity parameter.
>
> You also need the time required for the amplitude to reach its
> maximum in simple harmonic treatment, which is a quarter of
> the time it takes for one cycle to be completed (all cyclic motion
> can be mathematically represented by simple harmonic treatment).
>
> The frequency being the number of cycles per second, you obtain
> a quarter of one cycle in the following way
>
> t = 1 /(4 f)
>
> With a few simple transformations from simple harmonic
> treatment that I won't get into here, you get a simple
> equation that will allow you to calculate the amplitude
> of any photon you get curious about.
>
> A = c / (w cos(wt))
>
> A being your amplitude.
> c being the speed of light (299792458 m/s)
> w your angular velocity
> t is the time taken to reach 1/4 of one cycle
That makes
w * t = (2* pi * f) (1 / 4 * f) = pi / 2
and, cos(pi / 2) = 0. Thus, A is nfinite.
[Old Man]
> For the amplitude equation, just give a peek to the simple
> harmonic oscilation section of a textbook you might have
> on hand.
>
> A simple hand calculator will allow you to have quite a bit
> of fun
>
> André Michaud
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