# Homework Help: Help with microscope/telescope problems

1. Apr 25, 2004

### eku_girl83

This is part of a web assignment due tomorrow night, so I need help fairly quickly :)
Ok...I know the equations to use for these problems, I'm just really having trouble figuring out what's what from the wording of the problem.
1) The focal length of the eyepiece of a certain microscope is 16mm. The focal length of the objective is 6 mm. The distance between the objective and eyepiece is 19.7 cm. The final image formed by the eyepiece is at infinity. Treat all lenses as thin.
a) What is the distance from the objective to the object being viewed? Looking for s, but I have no idea how to do this...
1/f=1/s+1/s' but what are the focal length and the image distance?
I suppose s' would be negative, since image is virtual?
b) What is the magnitude of the linear magnification produced by the objective?
m=-s'/s
again, I need to find s' and s
c) What is the overal angular magnification of the microscope?
25s'/f1f2
Again, need s'

Ok here's the second one:
A telescope is constructed from two lenses with focal lengths of 96 cm and 12 cm, the 96 cm lens being used as the objective. Both the object being viewed and the final image are at infinity.
a) Find the angular magnification for the telescope.
I calculated this (correctly) to be -8.
b) Find the height of image formed by the objective of a building 60 m tall, 3 km away.
c) What is the angular size of the final image as viewed by an eye very close to the eyepiece?
No clue on parts b and c, so any insight would be appreciated...

Everyone on this forum has always been really helpful to me in the past. Thanks again!