[" If the image formed by a lens for all "],[" positions of an object placed in front of it "],[" is always erect and diminished,what is "],[" the nature of this lens? Draw a ray "],[" diagram to justify your answer.If the "],[" numerical value of the power of this lens "],[" is "10" D,what is its focal length in the "],[" Cartesian system? "quad " ICBSF-2nit? "]