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Homework Help: Lenses with eyes

  1. Feb 7, 2010 #1
    The focal length of a relaxed human eye is approximately 1.78 cm. When we focus our eyes on a close-up object, we can change the refractive power of the eye by about 16 diopters. Calculate the focal length of the eye when we focus closely.



    1/di+1/do=1/f



    im not really sure what to do with the diopters. please help me start the problem.
     
  2. jcsd
  3. Feb 7, 2010 #2
    A diopter is 1/f measured in meters. So 16 diopters would be 1/16 meters.
     
  4. Feb 7, 2010 #3
    alright so the 1.78 cm needs to be changed to .0178 m. do i need to incorporate that equation somehow or is this a really simple problem?
     
  5. Feb 8, 2010 #4
    someone please help. this homework is due tonight and i dont know where to go from here
     
  6. Feb 8, 2010 #5

    Redbelly98

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    Hope this isn't too late.

    A 16 diopter change means the following:
    The value of 1/f is changed by 16/m or 16 m-1
    You just need to figure out if 1/f would get larger or smaller, given that the eye is focusing on something close up.
     
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