Physics Help Forum Simple Mirror question whats wrong?

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 Jul 25th 2011, 10:40 PM #1 Junior Member   Join Date: Jul 2011 Posts: 2 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?
 Dec 16th 2011, 06:44 AM #2 Junior Member   Join Date: Mar 2009 Location: India Posts: 5 if you are sure about the method then maybe there is a misprint in the book
 Dec 19th 2011, 10:58 AM #3 Junior Member   Join Date: Jul 2011 Posts: 2 Thanks I'm quite sure its a misprint now. Just hoping to get a little reassurance.
 Dec 21st 2011, 02:05 AM #4 Junior Member   Join Date: Mar 2009 Location: India Posts: 5 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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# how far should an object be from a concave spherical mirror, of radius 36cm to form a real image one-nineh its size

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