# Lens Problems

1. Apr 16, 2004

### mustang

problem 24. A person looks at a gem using a concverging lense with a focal lenght 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?

Problem 32. A microscope slide is placed in front of a converging lens with a focal length of 3.48 cm. The lens forms an image of the slide 13.8 cm from the lens.
How far is the lens from the slide if the image is real? Answer in cm.

2. Apr 16, 2004

### Staff: Mentor

Your method is correct, but your answer is not. (Everything is correct except the last line.) Must have an arithmetic mistake. (Don't give so many significant figures in the answer: 3 is plenty.)

I get a slightly different answer for p. M is given, so what does that answer mean?