Express the power (with sign) of a concave lens of focal length 20 cm.

A convex lens forms an inverted image of size same as that of the object which is placed at a distance 60 cm in front of the lens.

Find —

(a) The position of image, and

(b) The focal length of the lens

The focal length of a convex lens is 25 cm. Express its power with sign.

A concave lens forms an erect image of 1/3rd the size of the object which is placed at a distance 30 cm in front of the lens. Find:

(a) The position of the image, and

(b) The focal length of the lens.