## EXERCISE 3. CELL SIZE MEASUREMENTS: OCULAR AND STAGE MICROMETERS

Figure 11: Micrometery.

### Materials

• Microscope

• Ocular micrometer

• Stage micrometer

• Millimeter ruler

• Prepared slide

### Procedure

1. Place a stage micrometer on the microscope stage, and using the lowest magnification (4X), focus on the grid of the stage micrometer.

2. Rotate the ocular micrometer by turning the appropriate eyepiece. Move the stage until you superimpose the lines of the ocular micrometer upon those of the stage micrometer. With the lines of the 2 micrometers coinciding at one end of the field, count the spaces of each micrometer to a point at which the lines of the micrometers coincide again.

3. Since each division of the stage micrometer measures 10 micrometers, and since you know how many ocular divisions are equivalent to 1 stage division, you can now calculate the number of micrometers in each space of the ocular scale.

4. Repeat for 10X and 40X, and 100X. Record your calculations below:

Microscope #

Value for each ocular unit at 4X

Value for each ocular unit at 10X

Value for each ocular unit at 40/45X

Value for each ocular unit at 100X

Using the stage micrometer, determine the smallest length (in microns) that can be resolved with each objective. This is the measured limit of resolution for each lens.

Compare this value to the theoretical limit of resolution, calculated on the basis of the numerical aperture of the lens and a wavelength of 450 nm (blue light).

Using the calculated values...

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Micrometers
Micrometers are instruments for precision dimensional gaging consisting of a ground spindle and anvil mounted in a C-shaped steel frame.  Noncontact laser micrometers are also available.
Optical Micrometers and Laser Micrometers
Laser micrometers measure extremely small distances using laser technology.
Dimensional Gages and Instruments
Dimensional gages and instruments provide quantitative measurements of product or component dimensional and form attributes such as wall thickness, depth, height, length, inner diameter (ID), outer diameter (OD), taper or bore.
Microscope Lenses and Objectives
Microscope lenses and microscope objectives include eyepieces or oculars, optical filters, objectives, adapters or mounts, condensers and other optical components for microscopy.
Reticles
Reticles are circular, transparent glass elements with a system of lines, dots, circles, or crosshairs for fine measurement or alignment in sighting applications.

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