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Homework Help: Looking at diffraction gratings .

  1. Mar 7, 2009 #1
    Looking at diffraction gratings.....

    Ok, so I got a question in my assignment.

    Monochromatic light of wavelength l is incident normally on a diffraction grating consisting of alternate opaque strips of width a and transparent strips of width b. The angle between the emerging zero order and second order spectra is given by?

    So I assumed that the slit separation is given by a since transparent strips (i assumed) is like those empty slits and slit separation is opaque.

    So I tried dsinθ=nλ. But my ans is sin^-1 2l/a.
    But the answer given is sin^-1 2l / (a+b)

    Is there a problem in my understanding of the question?

    EDIT: Is it because slit separation is calculated from the centre of each slit. Thus, the two 1/2 b will add together to get b, leading to slit separation a+b???
    Last edited: Mar 7, 2009
  2. jcsd
  3. Mar 8, 2009 #2


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    Hi qazxsw11111! :smile:
    Yup! :biggrin:
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