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Homework Help: Newton's Rings

  1. Mar 7, 2010 #1
    1. The problem statement, all variables and given/known data

    A plano-convex lens having a radius of curvature of r = 4.00m is placed on a concave glass surface whose radius of curvature is R = 12.0 m. Determine the radius of the 100th bright ring, assuming 500-nm light is incident normal to the flat surface of the lens.

    2. Relevant equations

    Kinda need to derive your own here. What I came up with was r - sqrt(r2 - s2) - R + sqrt(R2 - s2) = (m+.5)lambda/(2nfilm)

    s is the radius of the mth bright ring, lambda is the wavelength of light, nfilm is 1 for this problem since I assume the film is air

    3. The attempt at a solution

    Plugging in numbers I get this.

    I have no idea how to solve that equation without a calculator/computer, but I guess my answer would be 1.74 cm. Could be right, could be wrong.

    Any ideas on this? Thanks in advance.
    Last edited: Mar 7, 2010
  2. jcsd
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