Q. To focal length of a concave mirror is 12 cm. Where should an object length 4 cm be placed so that an image 1 cm long is formed?
A) 48 cm
B) 3 cm
C) 60 cm
D) 15 cm
Explanation
(c) $m = \frac{f}{f - u}$
$- \frac{1}{4} = \frac{- 12}{- 12 - u} = \frac{12}{12 + u}$
Or $12 + u = - 48\ \ $or$\ \ u = - 60\ cm$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.