Q13 of 45 Page 302

A real image, 1/5th the size of the object, is formed at a distance of 18 cm from amirror. What is the nature of the mirror? Calculate its focal length.

The magnification is given by



And the magnification is also given by



Now,





A real image is formed only for a concave mirror. Therefore,


The image length (v) =-18cm


According to the mirror formula,









Hence, the focal length of the concave mirror is 22.5cm


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