Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Double-Slit Question - PLEASE HELP

  1. Sep 9, 2005 #1
    Hi all,

    I am not educated in physics but truly need someone who greatly understands Young's Double-Slit Experiment to contact me directly at cteditions@aol.com. I need to figure out what size slits (and distances between slits) I need for a particular setup with a 4X5 camera. If I know the distance from the double-slit plate to the ground glass I need information on what I can expect as far as interference patterns.

    Since the double-slit plate will be mounted where the lens normally would be, what will happen when I move the lensboard closer and further from the ground glass?? I will be using natural light but can't I use a filter to make it monochromatic light? And what is best filter?

    This is NOT a school project. I need to get this information to the company that is cutting the slits!! I really need the HELP...

    Please help if you can.

    Much appreciation,

    Cody Thomas
  2. jcsd
  3. Sep 9, 2005 #2


    User Avatar
    Science Advisor

    You might have trouble doing this with natural light. If you use a broad-spectrum source, like natural light, all the different frequencies will have overlapping interference patterns and you won't clearly be able to distinguish between them.

    If you just try to filter it with a sufficiently narrow-band filter, you will probably find the intensity could be too low, depending on exactly what exposure time you plan for.

    I probably should have mentioned first that you will need to make the source coherent--natural light won't be. You would need to pass it through a single slit first, etc. If you don't know what I mean by this paragraph, then you are probably going to have to do quite a bit more preparation before you conduct this experiment.

    The particular slit characteristics you choose will depend on the frequency of light you choose and the specific geometry of your setup. You might find it easier to obtain the slits from a commercial educational scientific equipment supplier....

    It sounds like you are going to have to do a bit more preparation before you get to the point of having the slits cut.
  4. Sep 9, 2005 #3

    I know that I will need to use a filter so that the entire visible spectrum does not pass through the slits. And there is no problem with exposure as I do not need to "capture" anything in a quick manner.

    I understand that I will need a single slit in front of the double-slit but I need to have the double-slit cut first as it attaches to the lens mount of the camera... I can add a pinhole in front of the double-slit (at any distance necessary) at a later date.... I need help finding the size and spacing of the double-slits given a particular distance between double-slit and screen and a particular width/length of screen. PLEASE HELP ANYBODY.....

    Thanks again,

  5. Sep 10, 2005 #4
    Maybe these would help you calculate the numbers? :smile:

    The diagram appears when you start altering values, I think:

    http://schools.matter.org.uk/Content/Interference/laserinterference.html [Broken]

    The "s/mm", "b/mm" and "D/m" are just a fussy way of saying they mean "millimeters" for the distances between the slits, "millimeters" for the width of the slits and "meters" for the distance to the screen. :rolleyes:

    Anyhow, it shows you what you can expect when you alter the various distances.

    Scrolling down, here's a calculator for this kind of experiment as well:

    Last edited by a moderator: May 2, 2017
  6. Sep 11, 2005 #5
    Measure twice, cut once Codeman.

    Sound project management requires that you work out the details
    before you submit the purchase orders. This might be a lesson that's
    even more valuable to you than the diffraction of waves.

    P.S. Go to Edmund Optic's website and look for a green optical filter.
    You can use this but it won't be very bright because if you take white
    light and filter out a near-monchromatic color, it will be quite dim. That's
    why most folks use lasers. If you get a laser, be very careful with it. It
    can damage your eyes.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook