Question

the focal length of a concave mirror is 15cm. where should an object be placed so as to get its real image whose magnification is 3 times?
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Answer 1

Here, focal length of concave lens, f=-15cm. object distance, u=?, image distance, v=-10cm, magnification of lens, m=? Thus the object should be placed at a distance of 30 cm on the left side of the concave lens. Linear magnification, m=vu=-10-30=13.