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  4. Assertion: Magnification of a convex mirror is always positive, but that of a concave mirror may be both positive or negative. Reason: It depends on the sign convention chosen.

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Q. Assertion: Magnification of a convex mirror is always positive, but that of a concave mirror may be both positive or negative.
Reason: It depends on the sign convention chosen.

AIIMSAIIMS 2011Ray Optics and Optical Instruments

Solution:

The sign of magnification depend on the sign convention chosen. According to the new Cartesian sign conventions, magnification for a convex mirror is positive because image formed by a convex mirror is always virtual and erect. A concave mirror can form virtual or erect images and also real, inverted images. In the latter case, its magnification becomes negative. The reason though correct does not explain the assertion properly.