Physics

Problem

A student wants her compound microscope to give a maximum magnifying power of

400

. The tube length is fixed at

20\,\text{cm}

and the chosen objective lens has a focal length

f_o=0.5\,\text{cm}

. Taking

D=25\,\text{cm}

, which one of the following focal lengths of the eyepiece should she select? a)

2.5\,\text{cm}

3.57\,\text{cm}

2.8\,\text{cm}

2.55\,\text{cm}