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Homework Help: What is the focal length of the lens? given magnification and distance

  1. Apr 13, 2013 #1
    1. The problem statement, all variables and given/known data
    A biology student wishes to examine a bug at a magnificaiton of +5.00 by looking through a single lens. the student wants the image of the bug to be a distance of 25cm from the lens. what is the focal length of the lens?

    Answer:+6.25cm
    2. Relevant equations
    m=-d(image)/d(object)
    1/f=[itex]\frac{1}{d(object)}[/itex]+[itex]\frac{1}{d(image)}[/itex]


    3. The attempt at a solution
    first i solve for distance of object, d(object), by using the first equation:
    d(object) = (25x10-2)/5

    then i calculated focal length by using the second equation
    f = ((1/0.5) + (1/0.25))-1 = 0.041667

    i dont know what im doing wrong
     
  2. jcsd
  3. Apr 13, 2013 #2
    This is a simple magnifying glass using a converging lens.
    The image is VIRTUAL....what does this mean about the image distance in the equation???
     
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