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

power 4dAll 4D Real Time Live 4D Draw Results (Keputusan 4D) - Magnum 4D, Sports Toto 4D, Da Ma Cai, Sabah 88 Lotto 4D, Sarawak Special Cash Sweep 4D, STC 4D, SingaporeThe 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