Wednesday
July 30, 2014

Homework Help: Physics

Posted by Bob on Sunday, March 22, 2009 at 9:58pm.

A 2 cm object is placed 42 cm from a screen. Where should a converging lens of focal length 7 cm be placed between them to form a clear image on the screen? What two possible magnifications could the image have?

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1/do + 1/(42-do) = 1/7

do = -33.12 or -8.88
di = 42-do = 75.12 or 50.88

M = -di/do

= -75.12/-33.12 or -75.12/-8.88
= 2.27 or 8.46

= -50.88/-33.12 or -50.88/-8.88
= 1.54 or 5.73

I got 4 possible magnifications, but it said there was only 2. Did I do something wrong?

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