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Nature of photons presented in high school text books

  1. Nov 9, 2007 #1
    Why did textbooks (when I was in high school 5 1/2 years ago) always associate photons with the visible light part of the EM spectrum. Wouldn't the radio, x-ray, gamma, etc. areas of the spectrum exist as photons too?

    What about the transverse waves; would it not form a helix shape instead of the classic wave pattern on a flat plane? The former seems more realistic to me.

    Do photons REALLY exist? Think about it - a particle of which there would be a finite number of in the universe. A light source emits a certain number of photons per 3 dimensional degree. Eventually, wouldn't said photons diverge enough that would render the light source invisible to any telescope (because no photons are available to enter the lens). It makes me think that radiation energy exists as a longitudinal wave (like sound through matter medium) but with some other unseen, unfelt, unknown medium.

    Your thoughts?
     
  2. jcsd
  3. Nov 9, 2007 #2
    From what I recall, "light" has erroneously been equated to "visible light."

    I believe that in the simplest environment, a local vacuum, light waves (free photons) are sinusoidal and unpolarized.

    The photon model fits with the vast majority of experimental and theoretical physics, from quantum mechanics to general relativity, from electromagnetism to thermodynamics.
     
  4. Nov 10, 2007 #3

    russ_watters

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    Staff: Mentor

    I always thought "light" meant visible light. Ie, X-rays aren't light, they are x-rays. But all are forms of em radiation.
     
  5. Nov 10, 2007 #4
    "Light" is sometimes used for electromagnetic radiation just beyond visible light, i. e., "infrared light" or "ultraviolet light."
     
  6. Nov 10, 2007 #5
    i see what you mean by the point of no photons available to enter the telescope and what happens is light is not emitted by the start at any specific direction but photons are emitted at random directions every second or fraction of a second, and during this the photons emitted by the light reaches every possible region in the universe and since the number photons emitted is very large it looks like the star is emitting the photons in all directions, that is why sometimes the telescopes point at the same astronomical objects for seconds,minutes and sometimes hours.
     
    Last edited: Nov 10, 2007
  7. Nov 11, 2007 #6

    Claude Bile

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    Science Advisor

    Yes.
    You need to make a distinction between a classical wave (or the wavefunction of a photon if you like) and the internal field of the photon itself. You can get classical transverse waves and you can get classical helical waves (one just has a linear polarisation, while the other has a circular polarisation). Asking what the internal field of a photon however is like asking what the internal mass/charge distribution of an electron is - a question that, to me, doesn't make a great deal of sense.

    Yes.
    Probabilistically, the weaker a source the less photons per unit time will strike the detector. Thus the weaker a source, the longer we need to look to see a photon, which is a fairly well understood imaging principle. In practice our ability to detect a source is limited by the number of false positives (or dark counts) a photon counter tends to generate.

    Claude.
     
  8. Nov 12, 2007 #7
    In physics, the photon is the elementary particle responsible for electromagnetic phenomena.It is the carrier of electromagnetic radiation .
     
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