Optical Instruments

Objective:

In this exercise students will examine three optical instruments, a simple magnifier, a simple, refracting telescope, and a compound microscope.

Reference:

	From lenses to optical instruments
	Optical Instruments

Procedure:

Assume you have two thin lenses, one with a focal length of 10cm and one with a focal length of 2cm.

Part I: The simple magnifier

	Draw ray diagrams that show how to use these lenses as a a simple magnifiers. Draw these diagrams to scale.
	Fill in the table below. Are the images real or virtual?

Table I:

	Small lens	Large lens
x_i
x_o
M = -x_i/x_o
f

Part II: The simple telescope

The main purpose of a telescope is to gather more light from a distant objects than the unaided human eye. A simple Keplerian telescope consists of two converging lenses. The objective lens forms a real image of a distant object. The eyepiece acts as a magnifying glass. As you look through the eyepiece, you see an inverted, virtual image of the object.

	Draw a ray diagram that shows how to use the two lenses in a Keplerian telescope. Draw the diagram to scale.
	Fill in the table below.

Table II:

M=total magnification
d=distance between lenses

Part III: The compound microscope

The main purpose of a microscope is to produce a magnified image of a small object. Microscopes are almost identical to Keplerian telescopes except for the typical focal lengths of their objective lenses and the location of their objects.

	Draw a ray diagram that shows how to use the two lenses in a compound microscope. Draw the diagram to scale.
	Fill in the table below.

Table III:

	Objective	Eyepiece
Object distance
Image distance
Magnification

Total magnification

Both the telescope and the microscope use an objective and an eyepiece. Describe their similarities and their differences.

For up to 5 points extra credit, send send your answers and drawings to mbreinig@utk.edu .