The image obtained with a convex lens is erect and its length is `4` times the length of the object. If the focal length of lens is `20 cm`, calculate the object and image distances.

The image obtained with a convex lens is erect and its length is four times the length of the object. If the focal length of the lens is 20 cm, calculate the object and image distances.

The image obtained with a convex lens is erect and its length is 4 times the length of the object. If focal length of the lens is 20cm , calculate the object and image distances.

The image obtained with a convex lens is erect and its lenth is four times the length of the object.If the focal length of the lens is 20 cm,calculate the object and image distance.

The image obtained iwth a convex lewns is ereect and its length is four times the length of the object.If the focal length of the lens is 20 cm,calculate the object and image distance.

The image formed by the lens is erect and its length is three times the length of an object. If the focal length of the lens is 15 cm, what kind of lens it is ? Calculate the object and image distance.

If in a convex lens object and its image distances are each equal to d, the focal length of the lens is

An image of an object obtained by a convex mirror is n times smaller than the object. If the focal length of lens is f, the object distance would be ...........