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Value of theta of first minimum

  1. Sep 13, 2014 #1
    1. The problem statement, all variables and given/known data
    A parallel beam of monochromatic light of wavelength 580nm is incidentally normal on a diffraction grating. The separation between successive lines on the grating is 0.7μm as shown in the figure.
    please refer to the photo , i am having problem with part (a)


    2. Relevant equations



    3. The attempt at a solution
    my working is d sin θ = λ
    sin θ = λ /d , where d is the seperation between slits.. by plug in value of λ = 580x10^-9 and d = 1/ (5000x10^2) , i have my θ = 47 ° , the ans given is 56°
    why am i wrong?
     

    Attached Files:

  2. jcsd
  3. Sep 13, 2014 #2

    NascentOxygen

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    Where are you given that value for d?
     
    Last edited: Sep 13, 2014
  4. Sep 15, 2014 #3
    sorry i made a typo.
    here's what i mean :
    sin θ = λ /d , where d is the separation between slits.. by plug in value of λ = 580x10^-9 and d = 0.7x10^-6 , i have my θ = 47 ° , the ans given is 56°
     
  5. Sep 15, 2014 #4

    BvU

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    Part a asks about a single slit !
    And the distance between slits is NOT 70 micrometer.
     
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