Question

An object is placed at a distance of 1.5m from a screen and a convex lens is interposed between them. The magnification produced. Is 4 The focal length of lens is ;

• A. 1 cm
• B. 0.5 cm
• C. 0.24 cm
• D. 2 cm

Answer 1

Answer: (C)

0.24 cm

Answer 2

: Here, $\mathrm { m } = \frac { \mathrm { v } } { \mathrm { u } } = - 4$ or $u = \frac { - v } { 4 }$

Also,

$\frac { v } { 4 } + v = 1.5$ or or $\quad \theta = \cot ^ { - 1 } ( 0.75 )$ and