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Homework Help: Interference Problems

  1. Apr 18, 2004 #1
    Problem 3. A pair of narrow parallel slits separated by a distance of 0.274 mm are illuminated by the green component from a mercury vapor lamp (wavelength=545.5nm).
    What is the angle from the central maximum to the first bright fringe on wither side of the central maximum? Answer in degrees.
    Note: If the formula is: d(sin thetha)=m(wavelength)
    What do i do next??

    Problem 25.
    A diffraction grating is calibrated by using the 546.1 m line of mercury vapor. The first-order maximum is found at an angle of 26.09 degrees. Calculate the number of lines per centimeter on this grating. Answer in units of lines/cm.
    Note: How do I start?
  2. jcsd
  3. Apr 18, 2004 #2
    Problem 3:

    You have the equation:
    [tex]d \sin \theta = m \lambda[/tex]

    You have [tex]\lambda = 545.5 nm[/tex]

    You have [tex]d = 274 mm[/tex]

    The only additional fact you need is that the first bright fringe occurs where m=1.

    Solve for [tex]\theta[/tex].

    Problem 25.

    The same equation applies. Now you have to solve for d. d = the distance (center-to-center) between slits (lines). Once you know d you can find the number of lines/cm.
  4. Apr 19, 2004 #3
    Regards on problem 3

    So the problem is set up like this:
    d(sin thetha)=m(wavelength)
    274(sin thetha)=1(545.5)
    (sin thetha)= 545.5/274
    thetha= sin-1(1.9908)
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