Chapter 38, Problem 81PQ

A group of students is given two converging lenses. Lens A has a focal length of 12.5 cm, and lens B has a focal length of 50.0 cm. The diameter of each lens is 6.50 cm. The students are asked to construct a microscope from these lenses that has the same magnification as the telescope in Problem 80 if possible, and they have this discussion:

Avi: These are the same lenses we used to make a telescope. So they won’t work as a microscope. Microscopes are for looking at close objects; telescopes are for looking at far objects.

Cameron: All you need for a microscope are two converging lenses. I think the difference from a telescope is just that the order of the lenses is switched. A microscope is just a backward telescope.

Shannon: I think the order of the lenses doesn’t matter because the magnification is inversely proportional to both focal lengths. I think we have to adjust the distance between the lenses.

1. a. What do you think?
2. b. If a microscope can be constructed with these two lenses, describe its design. What is the minimum separation of the lenses? Where must you place the object?