A concave shaving mirror has a radius of curvature of 35 cm. It is positioned do that the image of a man’s face is 2.7 times the size of his face. We have to find the distance of the mirror from the man’s face.
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Solution: Click For PDF Version The lateral magnification, m, is given in terms of the image distance, ,
and the object distance, o,
by the relation
In a shaving
mirror the image will be erect. Therefore, image distance,
where o is the distance of the man’s face from the mirror (cm). The mirror equation is
In a concave mirror the centre of curvature is in the R-side. In the standard sign convention, textbook Physics by Halliday Resnick and Krane, the radius of curvature r will be positive. We thus have
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