A lens forms a virtual image `4 cm` away from it when an object is placed `10 cm` away from it. The lens is a ….. Lens of focal length ……………

Find the focal length of a convex lens which produces a virtual image at 10 cm from the lens when an object is placed at 5 cm from the lens .

A virtual image of an object is formed at 30 cm away from a lens when an object is kept at a distance 20 cm away from it . What is the focal length of the lens ? Find the magnification of the image ?

A concave lens produces an image 20 cm from the lens of an object placed 30 cm from the lens. The focal length of the lens is:

Find the focal length of a convex lens which produces a real image at 60 cm from the lens when an object is placed at 40 cm in front of the lens .

Find the focal length of a convex lens which produces a real image at 60 cm from the lens when an object is placed at 40 cm in front of the lens.

Find the focal length of a convex lens which produces a virtual image at 10 cm from the lens when an object is placed at 5 cm from the lens.

An object is placed at a distance of 12 cm from a convex lens on its principal axis and a virtual image of certain size is formed. If the object is moved 8 cm away from the lens, a real image of the same size as that of the virtual image is formed. The focal length of the lens in cm is