Question

draw a labelled ray diagram to locate the image of an object formed by a convex lens of focal length 20cm when the object is placed at 30 cm away from the lens​

Answer 1

Answer :

Focal length of convex lens is taken positive.

$:\implies\sf\:\dfrac{1}{v}-\dfrac{1}{u}=\dfrac{1}{f}$

$:\implies\sf\:\dfrac{1}{v}-\dfrac{1}{(-30)}=\dfrac{1}{20}$

$:\implies\sf\:\dfrac{1}{v}=\dfrac{1}{20}-\dfrac{1}{30}$

$:\implies\sf\:\dfrac{1}{v}=\dfrac{3-2}{60}$

$:\implies\:\boxed{\bf{\gray{v=60\:cm}}}$