Question

If a $3cm$ tall object placed perpendicular to principal axis of a convex lens of focal length $15cm$ produces a real invented image of height $15cm$, then its object distance $\left(u\right)$ is ................ and image distance $\left(v\right)$ is ................

• A. $u=-18m,v=+90m$
• B. $u=+18cm,v=-90cm$
• C. $u=-18cm,V=+90cm$
• D. $y=+18cm,v=+90cm$

Answer 1

Answer: (C)

$u=-18cm,V=+90cm$

$h_1=3cm$
$h_2=15cm$
$m=\frac{h_2}{h_1}=\frac{15}{3}=5$
As image is real and inverted
$m=-5$
object distance is always negative
$\therefore$ $u=-18cm$
and $v=+90cm$