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## Experiment: How Is the Microscope Used to Measure Small Objects?

#### Procedure:

A. Prepare a wet mount slide of a single piece of thread.

B. Place the wet mount slide on the stage. Observe under low power. Estimate the diameter of the thread

Question 1:

What is the diameter of your microscope field under low power in microns (µ)?

Question 2:

If the width of an object were half the field of view under low power, how many microns wide would the object be?

Questions 3:

What is your estimate of the diameter of the thread in microns? Count how many times Your thread would go across the field of view. Push your slide across. Divide this number into your field of view.

_______________________________microns      ________________________X power

C. Change your objective lens to medium and then high power. Focus with the fine adjustment if necessary.

Question 4: What is the diameter of your microscope field under medium power in microns (µ)

_______________________________microns      ________________________X power

Question 5: What is the diameter of your microscope field under high power in microns (µ)?

_______________________________microns      ________________________X power

Question 6: What is your estimate of the diameter of the thread under medium power in microns? High power?

(µ)_________________                                         __________100 X power medium

(µ)_________________                                         ___________400 X power high

Question 7: How does your estimate of the diameter of the cotton thread under high power compare to the estimated diameter under low power?

D. Prepare slides of wire, string, and human hair. microns of each, and record in Table 2. Estimate the diameter in microns of each, and record in Table 2.

#### Data and Observation:

Table 2: Measuring with the Microscope
 Material Diameter in Microns 40X                          100X                             400X thread wire string hair
Questions and Extensions:
1. Look at Table 2 and write a conclusion for this lab.
2. Explain how you would estimate the size of a micro-organism. Pretend you are using high power.

 These pages authored and maintained by Marcella Dawson. Revised 3/2002 . Copyright © 1995 CRPC GirlTECH. All rights reserved. . Email your comments. These pages were developed through GirlTECH '96, a teacher training and student technology council program sponsored by the Center for Research on Parallel Computation (CRPC), a National Science Foundation Science and Technology Center.