Calculate the focal length of a planoconvex lens?

AI Thread Summary
To calculate the focal length of a planoconvex lens producing a real image 2.5 times larger than the object located 2.5 cm from the lens, the lens formula 1/f = 1/v + 1/u is used. The object distance (u) is -2.5 cm, and the image distance (v) can be calculated as 6.25 cm based on the magnification of 2.5. Substituting these values into the formula gives 1/f = 1/6.25 + 1/-2.5, leading to a focal length of 1.25 cm after inverting the result. Clarification on the terms u (object distance) and v (image distance) is also sought, indicating potential confusion with different labeling in class. Understanding these concepts is crucial for solving lens-related problems accurately.
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Homework Statement



Calculate the focal length of a planoconvex lens that produces a real image 2.5 times as big as the object if the object is 2.5 cm from the lens?

Homework Equations



The only one I can think of is 1/f = 1/v + 1/u

The Attempt at a Solution


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My 'attempt' is 1/f = 1/62.5 + 1/25 = 0.056 but this just seems totally wrong.

Had a whirl at it, but cannot produce an answer, any help would be really appreciated!
 
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givemeknowledge said:
The only one I can think of is 1/f = 1/v + 1/u

I'm not familiar with u and v in these equations. I think my class labels them differently. What do they represent here?
 
You have to invert the answer to get f :)
 
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