(a) State the new Cartesian sign convention for lenses. (b) Define magnfication produced by a lens. How is it related to the object and image distance ?

(a) State the new Cartesian sign convention for lenses. (b) Define ma

1.	(a) State the new Cartesian sign convention for lenses. (b) Define magnfication produced by a lens. How is it related to the object and image distance ?
Answer» Solution :(a) As per new Cartesian SIGN convention for lenses : (i) All distances parallel to the principal axis are measured from the optical centre of the lens. (ii) Distances to the right of optical centre are taken positive and distances left to optical centre are taken negative. (iii) The heights measured above the principal axis are taken positive and those below the principal axis are taken negative. (B) The magnification PRODUCED by a lens is DEFINED as the RATIO of the height of image (h.) to the height of object (h). Magnification produced by a lens is related to distances u and v as : Magnification `(m) = (h.)/(h) = ("Distance of image from the lens (v)")/("Distance of object from the lens (u)")` Magnification of real, inverted image is negative. Magnification of virtual, erect image is positive.