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Homework Help: Single slit diffractoin

  1. Mar 27, 2013 #1
    Single slit diffraction

    1. The problem statement, all variables and given/known data

    Red light of wavelength 633nm from a helium-neon laser passes through a slit 0.390mm wide. The diffraction pattern is observed on a screen 3.00m away. Define the width of a bright fringe as the distance between the minima on either side.

    What is the width of the central bright fringe?

    What is the width of the first bright fringe on either side of the central one?

    2. Relevant equations

    asin(θ)= (m+1/2)λ

    3. The attempt at a solution

    I used the slit length, screen distance and wavelength to find the angle of the light.

    θ = arcsin([itex]\frac{λ}{2a}[/itex])

    Then I drew a triangle to find the length of the fringe.

    tan(θ) = [itex]\frac{h}{3}[/itex]

    h = 3tan(θ)
    h = .0024m

    I got .0024 for h but it is wrong.
    Last edited: Mar 27, 2013
  2. jcsd
  3. Mar 28, 2013 #2
    Are you familiar with the approximations to be used in a diffraction experiment?
  4. Mar 28, 2013 #3

    rude man

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    Gold Member

    Wrong formua. That one's for 2-slit interference, I think ...

    Grab the correct formula for the angular distance between minima for a single-slit Fraunhofer diffraction experiment. Realize that the central fringe comprises two minima, one on either side of the central maximum.
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