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Homework Help: Radius of curvature of second lens surface

  1. Aug 19, 2014 #1
    1. The problem statement, all variables and given/known data

    A lens of power of -5.0D has a surface which is convex of radius of curvature of 15.0cm. The lens is made of material of refractive index of 1.50.
    What's the radius of the other surface of lens?

    2. Relevant equations

    3. The attempt at a solution
    since power = 1/f
    so i have (1/ (-1/5) )= ( (1.5-1)/ 1) x ( (1/15) + (1/r2) )
    i found out my r2 = -0.10cm.
    But the correct ans given is -6.0cm.
  2. jcsd
  3. Aug 19, 2014 #2
    Here, lens of power = -5.0D. (1 Diopter = 1m-1)

    And you have taken the P = 1/f, here f is in "meter", but you have taken R1 = 15 cm which is in "cm."

    Don't you think this is weird.
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