A Compound Microscope Has a 18-Cm-Long Barrel and an Objective

Multiple Choice

A compound microscope has a 18-cm-long barrel and an objective lens with a focal length of 8.0 mm.What is the focal length of the eyepiece to give a total magnification of 240? It is adjusted for minimum eyestrain for persons with a near point of 25 cm.

A) 1.3 m
B) 1.5 cm
C) 1.9 cm
D) 2.1 cm
E) 2.3 cm