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Double Slit Experiment with White Light and one Slit colour filtered

  1. Jun 12, 2014 #1
    What would happen if the double slit experiment were to be undertaken using white light, and one of the slits was covered by a monochromatic filter (i.e. something which only one wavelength could pass through), and apart from this there was no detector monitoring which slit each photon was coming through?
    I think there are two possible scenarios:

    1. The wave interference pattern is visible for the colour of the filter, however the rest of the light would display a normal particle pattern behind the slit which was not filtered, it would not be white light, but would represent the white light if the wavelength of the monochromatic filtered light were removed from it.

    2. There would be no interference pattern and the particle pattern would appear on the screen, the light which came through the non filtered slit would be white, and the light which came through the filtered slit would be monochromatic.

    Please explain which, if either of these scenarios would occur, please explain why or why not
  2. jcsd
  3. Jun 12, 2014 #2
    What do you mean by this? The light coming through the slits will retain their property since there is no interference near the slits.
  4. Jun 12, 2014 #3


    Staff: Mentor

    Before going any further can you explain what you think each photon of white light is. In particular do you think each are the same?

  5. Jun 12, 2014 #4
    I understand that white light is made up of photons of different wavelengths
    Last edited: Jun 12, 2014
  6. Jun 12, 2014 #5
    Yes, that's what I mean in the second scenario. In the first scenario, the monochromatic light passing through the filtered slit interacts with the same wavelength going through the unfiltered slit. The other wavelengths of the white light are unaffected.
  7. Jun 12, 2014 #6


    Staff: Mentor

    That's correct - and random polarisations as well.

    That being the case the solution to your query is easy.

    If its the same wavelength as the colour filter of your slit you will get interference. If not it will not pass through that slit and you wont.

    It looks pretty trivial to me, which is why I asked the question.

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