A compound microscope has a magnifying power of 100 when the image is formed at infinity. The objective has a focal length of 0.5 cm and the tube length is 6.5 cm. Find the focal length of the eye- piece

detailed solution

Correct option is B

When final image is at infinity the magnification produced by eye piece is Dfe  and  ve=feL=vo+ue   1Vo+1uo=1fo6.5=Vo+fe    vou0+1=vofo                     u0vo+1=6.5−fe0.5Overall magnification  v0uoDfe=100                                            vouo=4fe                                    4fe+1=26.5−fe                                      4fe+1=13−2fe                                            6fe=12                                             fe=2cm