Focusing on Object K: Magnification & Adjustment of Focal Length

AI Thread Summary
To focus on object K, which is 1.69 m away, the focal length must change to approximately 41.07 mm, resulting in a change of about 0.975 mm. The magnification can be calculated using the formula M = -f2/f1. A miscalculation was identified in the initial attempt, where the placement of terms in the lens equation was incorrect. After correcting the equation, the problem was resolved, and the user expressed gratitude for the assistance. The discussion highlights the importance of careful equation setup in optics problems.
haxxorboi
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Homework Statement


Suppose the lens in a human eye has far focal length equal to f0 = 40.1 mm, for distant objects to be in focus.
A. An object K is 1.69 m from the lens. How much should the focal length change to focus on the object K?

B.What is the magnification ( = image size divided by object size) for the object K?


Homework Equations


1/di+1/do=1/f


The Attempt at a Solution


A. 1/1690+1/x=1/40.1
x=41.0746 mm
Thus, delta f = .9746 mm but that's wrong for some reason... but it's been a long week...

B. -f2/f1=M

Can someone help me out here?
 
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haxxorboi said:
1/1690+1/x=1/40.1
…
it's been a long week...

Hi haxxorboi! :smile:

Shouldn't the 1/x be on the other side? :redface:
 
*sigh* Yep, that'd be the issue... need either more sleep or more caffeine I guess...

Problem solved.

Thank you very much... I'm going to go take a nap...
 

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