1

We are used to measuring EMR energy as oscillations per second, but how are photons actually produced? what is the average number of pulses of same frequency , for example, the Sun produces of each frequency? does the stream of green light (for example: 530 THz) appear uninterrupted to a sensitive instrument?

Is there any particular reason to consider a photon as the number of oscillations per second? Would it be more 'realistic' to define a green photon by its own wavelength (566 nm) or duration (1.88*10^-15s) ?

  • 1
    Note that photons and light waves are not the same thing. If you're asking about statistical noise in black body radiation (the Sun's light is black body radiation) then that's an interesting question. But is you're asking if light is photons then that's been discussed before. – John Rennie Mar 11 '17 at 09:17
  • "average number of pulses of same frequency" The light is not pulsed but continuous, at all frequencies. – hdhondt Mar 11 '17 at 09:23
  • @JohnRennie, maybe I improperly used the term wave, by I was referring to a photon as an oscillation. If it wasn't clear , I am asking if the oscillations are produce individually, by the second or in a regular sequence, and if considering the frequency per second is totally arbitrary –  Mar 11 '17 at 09:23
  • @JohnRennie, if you reply, please clarify the terminology, can I say green light or shall I say green radiation or green photon? A green photon has 5.3*10^14 oscillations per second, but is one single oscillation still a green photon? –  Mar 11 '17 at 09:34
  • Each time an electron has a transition from a higher energy orbital to a lower energy orbital there's going to be an emission of a photon have $hf = \Delta E$ . Each frequency corresponds to different transitions inside different atoms or orbitals. The light from the sun consists of many of this "photons" from all the transitions etc that happen on the surface of the sun. We can identify the composition of the sun by inspecting how much of this each of the photons frequencies arrive to us - each corresponding to a specific orbital transition - quite unique. – Mihai B. Mar 11 '17 at 09:43
  • @MihaiB. nope. While there are lines from electronic transitions in sunlight the majority of the light comes from black body radiation not electronic transitions. – John Rennie Mar 11 '17 at 10:23
  • is one single oscillation still a green photon - no. Did you read the linked question? A photon is the quantum of energy exchange between the light and anything else. So green light exchanges energy in units of $h\nu$ where $\nu = 5.3 \times 10^{14}$. – John Rennie Mar 11 '17 at 10:26
  • @JohnRennie : https://en.wikipedia.org/wiki/Fraunhofer_lines ? https://en.wikipedia.org/wiki/Spectral_line ? https://en.wikipedia.org/wiki/Astronomical_spectroscopy ? – Mihai B. Mar 11 '17 at 10:29
  • @JohnRennie, thanks , that is the gist of my question: as you say, usually a green photon is considered the bulk of 5.3*10^14 oscillations, but the Sun (or any other source) does not produce oscillations in group /sequences of 5.3 per 10 ^14, does it? Isn't this grouping, definition an arbitray one? is the production/sequence of oscillations perfectly uninterrupted? if not, what is the average length of uninterrupted oscillations? –  Mar 11 '17 at 10:33
  • @lambertwhite: On the other hand the light propagate as in $ \frac{1}{c^2} \frac{\partial^2 \vec E}{\partial t^2} - \left(\frac{\partial^2 \vec E}{\partial x^2} +\frac{\partial ^2 \vec E}{\partial y^2} + \frac{\partial^2 \vec E}{\partial z^2} \right) = 0$ . A change in change of the electric field will cause a nearby change in the electric field. As you can see, the "magnitude" of change of change of $\vec E$ over time is called "frequency". The power received from sun at some distance is $P_{recv}(r)= \frac{P_{src} G c^2}{(4\pi r f)^2}$ – Mihai B. Mar 11 '17 at 10:36
  • 1
    To paraphrase John Rennie's excellent linked answer: "Light travels like a wave, and interacts like a particle, but it's all quantum fields, really." – PM 2Ring Mar 11 '17 at 12:05

0 Answers0