Question

A spherical mirror forms an image of magnification $3.$ The object distance, if focal length of mirror is $24cm$, may be

• A. 32 cm , 24 cm
• B. 32 cm , 16 cm
• C. 32 cm only
• D. 16 cm only

Answer 1

Answer: (B)

$m=\frac{f}{f-u}$
$3=\frac{-24}{-24-u}$ or $-24-u=-8$ or $u+24=8$
or $u=(8-24)cm=-16cm$
If $m=-3$, then $;-3=\frac{-24}{-24-u}u+24=-8$
or $u=-32cm$.