JEE Main 20268 Apr, Evening shiftPhysicsMediumOptics190× since 2002
A thin biconvex lens is prepared from the glass () both curved surfaces of which have equal radii of 20 cm each. Left side surface of the lens is silvered from outside to make it reflecting. To have the position of image and object at the same place, the object should be placed, from the lens at a distance of ______ cm.