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Old Jul 25th 2011, 10:40 PM   #1
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Simple Mirror question whats wrong?

Ok the question is from Schaum's outline:

How far should an object be from a concave spherical mirror of radius 36 cm to form a real image one ninth its size?

I come up with 1.8 meters the book has .18 meters. My work:

focal point = 18 cm All real images on this mirror are inverted thus from transverse magnification formula the distance of the image is the object distance divided by 9 (i= s/9).

Thus we get 1/s + 9/s = 1/18 which implies s (object) = 180 cm, which is 1.8 m.

What am I doing wrong?
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Old Dec 16th 2011, 06:44 AM   #2
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Cool

if you are sure about the method then maybe there is a misprint in the book
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Old Dec 19th 2011, 10:58 AM   #3
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Thanks

I'm quite sure its a misprint now. Just hoping to get a little reassurance.
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Old Dec 21st 2011, 02:05 AM   #4
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friend you are absolutly correct
The answer is misprint as
0.18 m = 18 cm
Focal length of the given mirror is 18 cm as we know images of objects placed at focus are same in size.
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