An object is kept at a distance of 100 cm from lens of power - 4 D

power 4dMagnum Corporation is the first company licensed to operate the exciting 4D Classic, including 4D Jackpot, 4D Jackpot Gold and Magnum Life. Social Responsibility Since inception in 1968,The power of a lens is +4D. Find the focal length of this lens. An object is placed at a distance of 50 cm from the optical centre of this lens. State the nature