Question

A convex lens produces a double size real image when an object is placed at a distance of $18$ cm from it. Where should the object be placed to produce a triple size real image?

• A. 44
• B. -16
• C. 22
• D. 33

Answer 1

The correct option is B -16

$Magnificationm=\frac{h_2}{h_1}\frac{-v}{u}=2-v=2\times (-18)v=36cmFromlensformulaweget\frac{1}{f}=\frac{1}{v}-\frac{1}{u}f=\frac{36}{3}=12cmtextFormagnificationm=3\frac{-v}{u}=3v=-3u\frac{1}{f}=\frac{1}{v}-\frac{1}{u}=\frac{1}{-3u}-\frac{1}{u}\frac{1}{12}=\frac{-4}{3u}u=\frac{-4\times 12}{3}=-16$