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Homework Help: Optics and images homework

  1. Dec 12, 2003 #1
    A real image is formed by a converging lens. It is three times higher than the object and inverted. the object and image are 1.00m apart. what is the focal length of the lens?

    I assume 3 = the magnitude...the 1.00 m is confusing me since its the total distance

    i tried using 1/p + 1/i = 1/f, to try to get the focal length....apparently its 18.8cm...
     
  2. jcsd
  3. Dec 12, 2003 #2
    Let p be the distance between the object and the lens, then the distance between the image and the lens is 3p since the magnification is 3.

    By applying
    1/p + 1/i = 1/f

    we have
    [tex]\frac{1}{p} + \frac{1}{3p} = \frac{1}{f} [/tex] ......... (1)

    Since the object and the image is 1m apart,
    p + 3p = 1 ....................(2)

    By solving (1) and (2), you'll get 18.75 cm.
     
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