question_answer

The plane faces of two identical plano-convex lenses each having focal length of 40 cm are pressed against each other to form a usual convex lens. The distance from this lens, at which an object must be placed to obtain a real, inverted image with magnification one is [NCERT 1980; CPMT 1981; MP PMT 1999; UPSEAT 1999]

A)            80 cm                                      

B)            40 cm

C)            20 cm                                      

D)            162 cm

Correct Answer: B

Solution :

                   To obtain, an inverted and equal size image, object must be paced at a distance of 2f from lens, i.e. 40 cm in this case.