[" A person needs a lens of power,"-5.5" D for correcting his distant vision.For correcting his "],[" near vision,he needs a lens of power,"+1.5" D.What is the focal length of the lens required "],[" for correcting: "],[" (a) distant vision? "],[" (b) near vision? "],[" What type of lens is being used for correcting (i) distant vision,and (ii) near vision? "]