Draw a labelled ray diagram to locate the image of an object formed by a convex lens of focal length 20 cm when the object is placed 30 cm away from the lens.
Given, f =20 cm, u = - 30 cm, v = ?
Using the lens formula, 1/v-1/u= 1/f
1/v=1/u+ 1/f =1/-30=1/20= 1/60
Therefore, v= 60 cm.
The labelled diagram as drawn: