photons

  1. I

    fields and photons?

    If photons travel in straight lines and do not interact with electric or magnetic fields. How can magnetic fields and electric fields be propagated by photons??? ie magnetic fields can both repel and attract depending on polarisation. Electric fields can depending polarity attract or repel...
  2. I

    Bare and Dressed Photons in space.

    Am I correct in thinking a "bare" photon in QED is represented as a qq- and a dressed photon is one that is absorbed and re-emitted via particle interactions as it passes through a medium. Does a bare photon as it passes through space interact with the zero point field and become dressed. ...
  3. P

    The attraction of massless particles to other massless particles and to matter

    I am really hoping someone might be able to offer a solution or at least offer guidance on something that is interesting me - are massless particles more attracted to particles with mass or other massless particles. A good example to work with could be photons: is light more attracted to...
  4. K

    Two photons and gravity

    If there were a universe containing only 2 photons would they attract each other (forgetting for the moment if such a scenario is even possible). That is would they exert a gravitational pull on each other. Or do they simply follow the pre-existing gravitational fields in the space-time...
  5. W

    Photons and Force

    Under Newtonian Physics we are taught that 'things' gain motion by the imparting of a force on such 'things.' What is the force that gives motion to a photon?
  6. I

    Max p.d of photons across p-n junction

    Photons with frequency 4.57x10^14Hz are incident on a p-n junction in a solar cell. What is the maximum potential difference these photons produce across this junction? I calculated E to be 3.03x10^-19 J but I don't really know where to go from here. I thought maybe E=1/2QV but I don't know...
  7. MBW

    Mass Gravity and Photons

    I know that photons follow the gravitational geodesic, but do they participate in generating the curvature of the geodesic? I am thinking toward the gravitational problems in cosmology where they are having to invent dark matter to account for the rotational behaviour of galaxies. If the...
  8. I

    Researches Concerning Photons as Corpuscles with Mass and Negative Electrostatic Char

    Conference: ICNRE 2015 : 17th International Conference on Nuclear and Radiation Engineering Tokyo, Japan, May, 28-29, 2015 http://waset.org/publications/10001894/researches-concerning-photons-as-corpuscles-with-mass-and-negative-electrostatic-charge Paper 67...
  9. K

    Why do photons change colour?

    If we shine white light on to a blue surface then only blue light is reflected and so we see the surface as blue. However, I am wondering about the bigger picture. I understand white is made up of multiple light frequencies, red, blue and green. These have different energies and we know E =...
  10. J

    Is This a Working Time Machine?

    This image was taken from this video https://www.youtube.com/watch?v=M1pCbM7s7Rs The answer will probably be no, but i am interested to know WHY this would/would not work. He is using a nonlinear crystal to create two entangled photons, one of which he is sending through the Einstein-Bose...
  11. J

    Question Related To The Delayed Choice Quantum Eraser Experiment

    I came across this article on Wikipedia: If i understood the experiment properly, idler photons that reach either D4 or D3 detectors are photons for which the "which path" is known and would consequently lead to their entangled signal photons at D0 not causing any interference 8ns BEFORE...
  12. P

    Photons and Black Holes

    Sorry if this seems like a dumb question and many of my assumptions based on my understanding here may be wrong. I always hear about how light cannot escape a black hole. Can light even enter a black hole in the first place? I've seen examples where massive objects can bend light and I'm...
  13. Anonymous

    How can we see things that don't emit photons?

    How can we see things that don't emit photons? Photons is what the eye makes signals of to the brain, right? And how come things have different colors? Thanks
  14. F

    Teaching modern physics

    Why does nobody show the rather elegant way of deriving Planck's radiation law a la Bose. In several books I found a short derivation entitled "application of Bose Einstein statistics". But when it comes to computing the state density of the photons they resort to classical ED counting modes...
  15. muon321

    Photons And Electromagnetic Waves

    How many photons correspond to a single electromagnetic wave? Is there more than one photon for each wave?
  16. U

    How come photons travel at the speed of light?

    Sounds like a silly question but hear me out. A photon has energy, right? And isn't energy equivalent to mass? An object with mass cannot travel at the speed of light. However a photon (being a quanta of light) can travel at the speed of light. How is this possible due to mass-energy...
  17. E

    Question about light speed

    Since photons travel so much faster than any body we measure, and photons are detected the instant one reaches a moving detector, why expect that the source speed or detector speed to have any affect at all on the measurement of C? I would assume that during the short interval that a photon is...
  18. G

    Question on photons and a question on speeds of electrons.

    1. Find the max KE of photoelectrons emitted when a metal of work function 2.8 eV is exposed to photons of wavelength 3 x 10 Express your answer in Joules and eVs. If these electrons are the accelerated through 100 volts in a vacuum what will their final max KE be (i) in eVs (ii) in Joules...
  19. L

    Photons or wave trains? The error of Alain Aspect.

    In 1986 the French physicists Grangier, Roger and Aspect have made the decisive experiment to give the direct answer to a key question of quantum physics – does the light consist of photons or of wave trains? In this experiment the radiation passed through "beam-splitter": semitransparent...
  20. A

    Basic question on Photons

    A question which we had in a test. 1)The power output of a source of light emitting photons of a fixed frequency is increased. How does the number of photons per unit volume in the beam change? 2)What will happen to the number of photons per unit volume if the frequency is increased keeping...