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Homework Statement
An object 0.6cm tall is placed 16.5cm to the left of the vertex of a concave spherical mirror having a radius of curvature of 22.0cm.
Determine the position, size, orientation and nature of the image.
Homework Equations
[itex] \frac {1}{S} + \frac {1}{S'} = \frac {1}{f} = \frac {2}{R} [/itex]
The Attempt at a Solution
[itex] \frac {1}{16.5}+ \frac {1}{S'} = \frac {2}{-22} [/itex]
[itex] \frac {1}{S'} = -\frac{1}{11} - \frac {1}{16.5} [/itex]
[itex] S' = -6.6cm [/itex]
However, the answer given is 33.0cm, which you get when R = +22.0 , not -22.0
In my lecture notes is definitely says that the radius of curvature for a concave mirror is negative.
Are the notes wrong? Or is there something I am missing?
(Using 33.0cm as S' I can get the answers to the other parts of the question, I just want a little bit of help in understanding why the radius of curvature is positive)
Thanks