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Angular Magnification

by A_lilah
Tags: angular, magnification
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A_lilah
#1
Jun7-10, 12:41 AM
P: 53
1. The problem statement, all variables and given/known data
If you have normal vision and are properly using a magnifying glass with a refractive power of 12.5 diopters, how far should you hold it from the object to achieve maximum angular magnification?


2. Relevant equations

1 diopter = 1/focal length = m^-1
M=angular magnification
Mmax = [(Near Point)/f] +1
Near point for someone with normal vision = 25cm

3. The attempt at a solution

First I use 12.5 diopters to figure out the focal length:

1/12.5 = .08m = 8cm
Then I plugged this into the equation for Mmax for someone with normal vision:
[25cm / 8cm] + 1 = 4.125 = Mmax

I don't know how to use any of this to find the maximum distance the object should be held at though. The prof already posted the answers-this should be 6.67 cm- I'm just trying to practice before an exam and learn how to do this, so any help/tips would be great. Thanks!
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Nax13
#2
Jun9-10, 11:14 AM
P: 4
Maybe you can use this:

M = (f-v)/f

4.125 = 8-v/8

v = 25cm

I am not so sure abt the answer. Another formula that you might find useful is M = f/(f+u)


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