Q. A point object is placed on the axis of the concave mirror at a distance of $60\ cm$ from the focal point of the mirror. Its image is formed at the point of object, then focal length of the mirror is
A) 15 $cm$
B) 30 $cm$
C) 60 $cm$
D) 120 $cm$
Explanation
(c) Since the image is formed at the point of object $i.e.,$ object is kept on the radius of curvature
$\therefore C.F. = F.P. = 60\ cm = f$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.