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

  • Thread starter RedLego
  • Start date
  • #1
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Homework Statement


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

Homework Equations


m=-d(image)/d(object)
1/f=[itex]\frac{1}{d(object)}[/itex]+[itex]\frac{1}{d(image)}[/itex]


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
 

Answers and Replies

  • #2
1,506
18
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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