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Homework Help: Find the distance d that places the final image at infinity.

  1. May 12, 2004 #1
    Anyone know how to solve the following problems? Thanks!

    1.) An object is placed 12 cm to the left of a diverging lens of focal length
    -6cm. A converging lens of focal length 12 cm is placed a distance of d to the right of the diverging lens. Find the distance d that places the final image at infinity.

    2.) Light of wavelength 460 nm falls on a diffraction grating with 5000 slits per cm. What is the required ditance from the slits to a screen if the spacing between the first and second dark fringes is to the 0.7m?
  2. jcsd
  3. May 13, 2004 #2

    Doc Al

    User Avatar

    Staff: Mentor

    The first problem is a straightforward application of the lens equation:
    [tex]\frac{1}{f} = \frac{1}{o} + \frac{1}{i}[/tex]

    The second problem requires the equation for diffraction:
    [tex]d sin\theta = m \lambda[/tex]

    To learn what these equations mean and how to use them, consult your text.
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