Vocabulario Pelicula De Los Simpsons

Calibration of the Ocular Micrometer on a Microscope

Microscopes are often used to measure small objects. For instance, forensic scientists use microscopy to measure the distance betweenmicroscopic tool marks or the diameter of fibers. As you can see in figure 1 below, compound microscopes have ocular micrometers, or rulers that can help you measure items under the microscope. However, thescale on the ocular micrometer changes with total magnification, and thus has no absolute value. Therefore, the ocular micrometer does not have units and it needs to be calibrated prior to use. Inthis activity, you will learn how to calibrate the ocular micrometer, a skill that will help you in next week’s microscopy lab.

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Figure 1: Ocular micrometer superimposed over a view of red blood cellsunder the microscope.

You will use a stage micrometer to calibrate the ocular micrometer. A stage micrometer is essentially a ruler that is mounted on a microscope slide that does have units(millimeters (mm) or micrometers (μm)). When calibrating, you will line up the stage micrometer with the ocular micrometer and count the number of divisions on the ocular micrometer per millimeter ormicrometer on the staged micrometer. The number of divisions will change as the magnification changes.

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Figure 2: Comparison of the ocular micrometer and the stage micrometer.

Example: At atotal magnification of 40x, a student measured 42 ocular micrometer divisions per millimeter. What is the distance in micrometers per ocular unit?

[pic]23.8 μm per ocular unit

Problem1: At a magnification of 40x, a student measured 41 ocular micrometer divisions per millimeter. What is the distance, in micrometers, per ocular unit at 40x?






Problem 2: At a total...