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Single Photon Double Slit Experiment

  1. May 27, 2004 #1
    I have decided on a physics experiment for highschool, but am not sure how to go about doing it, and what materials to use :confused: . Its called the Single photon Double Slit Experiment, similar to the one done by GI Taylor, years ago.

    the basic concept is that a single photon is emmited into a screen with two slits and it goes through to a photographic plate where over time produces an interference pattern similar to one from a youngs experiment with light.

    If anyone has any ideas or if you have done the experiment yourself please help :wink: . A simple setup would be great because i have so much on my plate atm. Any extra information that could help would be excellent. thanx
  2. jcsd
  3. May 27, 2004 #2


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    Try this:

    http://www.optica.tn.tudelft.nl/education/photons.asp [Broken]

    Last edited by a moderator: May 1, 2017
  4. May 27, 2004 #3
    I did this experiment a few years ago at university. We used a laser, optical filters to absorb the light, two slits (obviously) and a very sensitive photomultiplier for detection.

    If you are in highschool, then you probably won't have all of this equipment. You can replace the laser with any monochromatic source, I believe a sodium light was used in the original experiment. It will probably need to be collimated by placing a single slit before the double slit. You can use photographic film to do the detection and run the experiment for varying lengths of time to show how the interference pattern gradually gets built up.

    Doing the experiment this way will require very long runs, so I hope you have a good few weeks to get it finished. I also hope that you enjoy spending large amounts of time in total darkness.
  5. May 27, 2004 #4


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    What is the significance of using a single photon if you're going to let the pattern build up anyway? Would it be feasable for you to use a ccd or something that can register a single photon in quasi-real-time? That way, you could have a computer display the individual hits while alongside this display you could show the accumulation (or, you could have the accumulation as some faded or outrigth different colour and have the individual hits register on the display as a different colour superimposed).
  6. May 27, 2004 #5
    The significance of a single-photon experiment I guess is to convince the experimenter that the interference pattern is not produced by the interaction between different photons but by each photon interfering with itself, which gives a hint that the photon went through both slits, or at least the wave did.
    I don't think a highschool student would typically have or be able to purchase and put together the equipment needed for real-time detection. On the other hand, if you reduce the intensity of the light enough, you can assume that most photons arrived at different times.
  7. May 27, 2004 #6


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    Yeah, I suppose you could run the experiment at a low intensity for a very brief duration, and then gradually increase this duration, showing the photographic film developing one, then two, then three dots, etc. Then, you could run it once for a very long duration showing the development of the pattern.
  8. May 31, 2004 #7
    thanks everyone...your help has been great....if you have any extra information that might help please feel free to add it...
  9. Jun 3, 2004 #8
    this experiment is best done with electrons, sice their charge can be detected, but since you must use light, I would suggest you lower the intencity of your source untill only one photon is emmited at a time. But I doubt you have the kind of technology that will tell you when this is acheved. Good Luck :biggrin:
  10. Jun 7, 2004 #9
    hey every1
    I am doing an experiment at school based on Youngs double slit experiment. I was wondering if it would be worth my time to look at the interference cathode rays have in a similar way.
  11. Jun 7, 2004 #10
    The electron diffraction experiment is a lot more difficult to do than the one with light. This is mainly due to the fact that the de-Broglie wavelength of an electron is extremely short, which means that the whole experimental setup needs to be minaturised to see the same effect. To see this, use the formula for the de-Broglie wavelength [tex]\lambda = \frac{h}{p}[/tex], where p is the momentum and h is Planck's constant, and compare with typical wavelengths of light. This is probably beyond the technology you have available in school.

    However, to see electron diffraction, the best way is to fire the electrons into some sort of crystal. The structure of the molecules acts like a diffraction grating. In fact, you can tell a lot about the structure of the crystal from the diffraction pattern that you see.

    The other problem is that you need to select electrons that have the same energy. This is equivalent to the fact that Young's experiment only works with monochromatic light. This can be done using a rotating disc with a narrow slit cut in it, so that only electrons in a narrow range of velocities can get through.
  12. Jun 8, 2004 #11
    thanks alot for the help man. it answered my question and gave me a bit more to think about. Thanks again
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