Measuring Techniques D1 Part I: Measuring the Size of a Specimen Using the Field of View Technique.

Preface: Before beginning this module, you should be familiar with the parts, use, and care of the compound microscope. Before beginning this module, you should be familiar with the parts, use, and care of the compound microscope. If you are unsure about the microscope’s operation, please review the Use of the Microscope module. If you are unsure about the microscope’s operation, please review the Use of the Microscope module.Use of the MicroscopeUse of the Microscope Mishandling of the microscope can lead to damage of the instrument. Mishandling of the microscope can lead to damage of the instrument.

Module Requirements: To complete this module, the following equipment will be provided to you by an SLC assistant. To complete this module, the following equipment will be provided to you by an SLC assistant. -microscope workstation -prepared microscope slide -stage micrometer -worksheet If materials are missing or you are having problems getting started, please ask one of the SLC staff for help.

Module D1: Objective The completion of this module will allow you to use the Field of View Technique in order to measure length, width, diameter and other linear dimensions of a microscope specimen. The completion of this module will allow you to use the Field of View Technique in order to measure length, width, diameter and other linear dimensions of a microscope specimen.

Of all the microscope measuring techniques covered at the Science Learning Center, the Field of View Technique is the least precise. Of all the microscope measuring techniques covered at the Science Learning Center, the Field of View Technique is the least precise. Use the Field of View Technique only when approximate measurement is adequate, and the specimen’s size is 30 to 4500 microns. Use the Field of View Technique only when approximate measurement is adequate, and the specimen’s size is 30 to 4500 microns.

Procedure: 1. Chose the objective lens that is appropriate for your specimen. At this point, adjust your microscope, selecting the 10X objective lens. Turn and lock into place

Procedure Continued: 2. Obtain a stage micrometer. The Science Learning Center uses 2mm micrometers divided into units of 0.01 mm.

Procedure Continued: 3. Position the stage micrometer on the microscope’s stage and clearly focus the scale using the 10X objective lens. Note: If you are having trouble finding the scale at 10X, switch to a lower power, such as 4X, to center scale. Then select the 10X objective and use the fine adjustment to focus.

Procedure Continued: 4. Measure the diameter of the field of view. To make your measurement, line up one end of the stage micrometer scale with the edge of your field of view. Adjust your microscope now. To make your measurement, line up one end of the stage micrometer scale with the edge of your field of view. Adjust your microscope now. Example

Procedure Continued: With the micrometer lined up in your field of view, measure the diameter to which your eye can see within the illuminated area. With the micrometer lined up in your field of view, measure the diameter to which your eye can see within the illuminated area. Note: At this point do not adjust your stage. Note: At this point do not adjust your stage. Write down your measurement on a piece of scrap paper. Write down your measurement on a piece of scrap paper.

Procedure Continued: You should have found your workstation microscope field of view to measure in a range between 1.66 and 2.06 mm. You should have found your workstation microscope field of view to measure in a range between 1.66 and 2.06 mm. If your results are different, please go through the procedure again. If your results are different, please go through the procedure again. If problems remain, please ask an SLC representative for assistance. If problems remain, please ask an SLC representative for assistance.

Notes: When we measured the field of view, we took the diameter of the “circle” that we could see using our microscope. That distance may vary from scope to scope due to calibration, manufacture, and of course human error. When we measured the field of view, we took the diameter of the “circle” that we could see using our microscope. That distance may vary from scope to scope due to calibration, manufacture, and of course human error. For this reason, we must include an uncertainty with our measurement. For this reason, we must include an uncertainty with our measurement.

Calculating the Uncertainty The uncertainty of your measurement can be given as +/- one tenth (0.1) of the diameter of your field of view measurement. The uncertainty of your measurement can be given as +/- one tenth (0.1) of the diameter of your field of view measurement. Example: My field of view measurement is 1.85 mm. So my uncertainty would equal +/ Therefore, if the length of my specimen is 1.255mm and I have an uncertainty of I can say that actually the specimen measures between mm and mm. Therefore, if the length of my specimen is 1.255mm and I have an uncertainty of I can say that actually the specimen measures between mm and mm.

Try It! 1. Remove the stage micrometer. 2. Place your sample specimen on the stage. 3. Focus 4. Estimate the area covered by your specimen. For example, we have drawn imaginary lines across our field of view to show that the size of this stone is 1/3 of our field of view.

Try It! 5. Calculate the size of the specimen by multiplying the fraction of the field the specimen covers, times your field of view. Don’t forget your uncertainty! For example: Our specimen covers 1/3 of the field of view. The initial field of view measurement was 1.85 mm. The calculation would be: For example: Our specimen covers 1/3 of the field of view. The initial field of view measurement was 1.85 mm. The calculation would be: (0.333)x(1.85) = mm +/-.185 mm (0.333)x(1.85) = mm +/-.185 mm

Important If you change to a different objective lens, the field of view will be different than the measurement you have taken for the 10X objective. If you change to a different objective lens, the field of view will be different than the measurement you have taken for the 10X objective. Naturally, the field of view decreases with greater magnification. Naturally, the field of view decreases with greater magnification. Therefore, if you must change the power of the objective lens, you must determine the diameter of the new field of view. Therefore, if you must change the power of the objective lens, you must determine the diameter of the new field of view.

Measurement Conversion In some cases you will be required to convert your measurements to a smaller size. In some cases you will be required to convert your measurements to a smaller size. A useful conversion to remember is millimeters (mm) to microns (μm). A useful conversion to remember is millimeters (mm) to microns (μm) μm = 1 mm 1 μm = 0.001mm

Measurement Conversion Let’s use our earlier example to perform a measurement conversion. Our specimen covers ½ of the field of view. Our initial field of view measurement was 1.85 mm. Your calculation was. Let’s use our earlier example to perform a measurement conversion. Our specimen covers ½ of the field of view. Our initial field of view measurement was 1.85 mm. Your calculation was. (0.5)x(1.85mm) =.925 mm +/-.185 mm (0.5)x(1.85mm) =.925 mm +/-.185 mm (0.5)x(1850μm) = 925 μm +/ μm Note: do not forget to convert your uncertainty to get your final answer.

Module Completed! Please return to the main desk to obtain a post test from your friendly Science Learning Center personnel. Please return to the main desk to obtain a post test from your friendly Science Learning Center personnel.