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## Homework Statement

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?

## Homework Equations

1 diopter = 1/focal length = m^-1

M=angular magnification

Mmax = [(Near Point)/f] +1

Near point for someone with normal vision = 25cm

## 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!