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About Newtion ring experiment

  1. Apr 19, 2016 #1
    1. The problem statement, all variables and given/known data
    擷取3.PNG
    refractive index of prism=1.45
    λ=450nm
    50 bright ring are observed
    find d


    2. Relevant equations
    2d=nλ/2

    3. The attempt at a solution
    since 50 bright rings are observed n=24 (-24---------0-------------24)
    if the distance travel=λ/2 constructive interference will happen
    since the ray1 reflected by prism(n=1.45--->n=1 air)no phase shift
    by ray 2 air to flat plate have phase shift

    2d=24(λ/2) and λ=450nm/n=450nm/1.45=310nm
    d=[310nm(24)]/4=1.86x10^-6m but the answer=1.11x10^5m why?????
     
    Last edited: Apr 19, 2016
  2. jcsd
  3. Apr 19, 2016 #2
    i think
    for constructive interference -draw a diagram of the rays interfering at thickness d
    the correct condition perhaps is
    path difference = n. wavelength (in phase)
    and path difference =2.d + (wavelength / 2)
    check from your text book
     
  4. Apr 19, 2016 #3
    so do you mean nλ=2d+
    why pd=2d+λ/2?
     
  5. Apr 19, 2016 #4
    draw the ray diagram for interference
     
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