• # question_answer Image formed by a concave mirror of focal length 6 cm, is 3 times of the object, then the distance of object from mirror is                     [RPMT 2000] A) - 4 cm                                     B) 8 cmC) 6 cm                                         D) 12 cm

m = ± 3 and f = ? 6 cm Now $m=\frac{f}{f-u}\,\,\,\Rightarrow \,\,\pm 3=\frac{-\,6}{-6-u}$ For real image $-\,3=\frac{-\,6}{-6-u}$  Þ $u=-\,8\,cm$ For virtual image $3=\frac{-\,6}{-6-u}$ Þ $u=-\,4\,cm$