Question

A magnifying glass has f=12 cm Where shall an object be placed to produce maximum angular magnification? Least distance of clear vision = 25 cm

• A. 7.1 cm
• B. 6.8 cm
• C. 8.4 cm
• D. 8.1 cm

Answer 1

The correct option is D 8.1 cm

Given least distance of clear vision $=25cm.$

Therefore, image is formed at a distance of 25cm from lens.

The lens makers formula is $\frac{1}{v}+\frac{1}{u}=\frac{1}{f}$

where

u=distance of object from lens.

v= distance of image from lens

f= focal length of lens.

Since magnifying lens is convex focal length is positive.

Given conditions are $v=-25$ and $f=+12,$

Substituting in the above equation we get

$u=8.1cm$ from the lens on the same side of image.