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What Affects the Energy of a Photon?

  1. Jun 20, 2010 #1


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    I asked my physics teacher what affected the energy of a photon. He said that it was only the frequency, and nothing else. However, I don't understand this.

    E = hv (I'll say E = hf to make it simpler to avoid confusion) states that the energy of a photon is equal to Planck's constant multiplied by the frequency of the wave.

    However, frequency is equal to velocity over wavelength due to v = fλ. So this means that;

    [tex]E = \frac {hv} {\lambda}[/tex]

    Meaning that frequency, wavelength AND velocity affect the energy of a photon. Is this true or is my physics teacher correct?

  2. jcsd
  3. Jun 20, 2010 #2
    I would say your teacher is correct. Assuming the photon is in a vacuum, it always travels at the speed of light, c. Then you know,


    so if I give you the wavelength of a photon, you automatically know what the frequency is--they are dependent on each other.
  4. Jun 27, 2010 #3


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    Thanks, that makes sense. So it is definitely only wavelength and frequency (and photons per second) that affect the intensity of light?
  5. Jun 27, 2010 #4
    Photons per area per second, otherwise yes.
  6. Jun 27, 2010 #5
    If i were to travel at the photon at a certain speed , the Doppler effect would come into play and i would perceive the photon as a different frequency so if i traveled fast enough i could make red light look green , i wonder if that would hold up in court for blowing a red light , then they would just give me a speeding ticket anyway , And also gravitational fields affect the frequency of the photon ,
  7. Jun 27, 2010 #6


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    Well, if they don't fine you for running through the red light, they could certainly fine you for speeding!
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