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

Focal length of convex lens is taken positive.

`:\implies\sf\:(1)/(v)-(1)/(u)=(1)/(f)`

`:\implies\sf\:(1)/(v)-(1)/((-30))=(1)/(20)`

`:\implies\sf\:(1)/(v)=(1)/(20)-(1)/(30)`

`:\implies\sf\:(1)/(v)=(3-2)/(60)`

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