power 4dTwo lenses have power of (i) + 2 d (ii) -4D. What is the nature and focal length of each lens? b. An object is kept at a distance of 100 cm from lens of power -4D. Calculate the image distance.Use the power of 4D to optimise your schedule with a fully integrated module making it easy to generate 4D plans. Learn more . 4D planning will transform your operation – read about