Converging lens focal length and magnification problems

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Lens Problems
problem 24. A person looks at a gem using a concverging lense with a focal length of 13.7 cm. The lense forms a virtual image 35.5 cm from the lense.
a) Find the magnifaction.
This is what I have done so far:
f=13.7 , q= -35.5
1/p+1/q=1/f
1/f-1/q=1/p
1/13.7-(-1/35.5)=9.88516=p
M=-q/p
=--35.5/9.88516
= 4.02333

Is this right??

Problem 30. A magnifying glass has a converging lens of focal length 17.4 cm. At what distance from a nickel should you hold this lens to get an image with a magnificaiton of +2.06? Abswer in cm.
got p=8.7 and M=1.841932169 is this right?
 

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You posted this same problem in College Help.
 


Yes, your calculations for both problems 24 and 30 are correct. For problem 24, the magnification is approximately 4.02, meaning the virtual image is 4.02 times larger than the object being viewed. For problem 30, the distance from the lens to the object (nickel) is approximately 8.7 cm. This means that the object should be held 8.7 cm away from the lens to achieve a magnification of +2.06. Great job!