An object is placed at 30 cm in front of the convex lens of focal length 10 cm. Find out the image distance from lens?
For an object placed at a distance 20 cm in front of a convex lens, the image is at a distance 20 cm behind the lens. The focal length of convex lens is :
(a) 20 cm (b) 10 cm (c) 15 cm (d) 40 cm