[单选题]
A compound microscope has a 18-cm barrel and aos 4cdu qnvh )i*d67u7n objective with a focal lengthji p ,7rka8fi bdac04. of 8.0 ic8 fa,drbk.704i jpa mm. What is the focal length of the eyepiece to give a total magnification of 240?
A. $0.13 \; cm$
B. $1.5 \; cm$
C. $1.9 \; cm$
D. $2.3 \; cm$
Post time 2024-1-26 22:03:25