1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Uncertanty in double slit diffraction

  1. Mar 13, 2012 #1
    In a double-slit experiment electrons are sent through a doule slit where an indicator determines the slit each electron went through. These indicators tell the y coordinate to within d/2, where d is the distance between the slits. If this is the case show that the diffraction pattern will be destroyed.

    The angular distance,Δθ, between a maximum and minimum is λ/(2d). The angular distance may also be approximated as Δy/l where l is the distance from the slits to the screen. The y seperation,Δy, at the screen between a max and adjacent minimum is (λl)/(2d).

    I understand that in order for the pattern to be destroyed the uncertainty in the y position at the screen must be equal to the distance between adjacent min and max, but I can't seem to get there.

    The uncertainty of y at the slits is given in the problem as d/2 allowing the momentum in y to be found. Assuming the uncertainty in p at the slit is the same at the screen then Δp is known. Assuming the electron has a momentum in the x direction then the momentum in x and the wavelength may be used. I tried to say that Δθ=Δy/l, and then substitute the p relation in for y but this gets me no where. Messing around I found out that setting Δy/l=Δpy/px and solving for Δy gives the correct relation but I have no idea why you can set these two things equal to each other.
  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Can you help with the solution or looking for help too?
Draft saved Draft deleted

Similar Discussions: Uncertanty in double slit diffraction
  1. Young's double slit (Replies: 0)