Most people use put a transparent plastic ruler under microscope to perform this task. Actually, the microscope itself provides pretty accurate measurements ranging from 0.2 - 10 mm. Based on optical physics, the diameter of the field of view can be reliably derived by a simple formula: Show Diameter of the field of view (mm) = F / M, where F is the number of field of view (FOV) of the eyepiece, and M is the magnification (mag.) of the objective. For example: Diameter of the field of view (mm) = 20 / 40 = 0.50, where 20 is the field number of eyepiece, and 40 = objective mag.
Most modern microscopes have eyepieces with the number of field of view at 20 or 22. The diameters of the field of view are listed:
* Magnification ofocular lens10______________uni00D710______________uni00D710______________uni00D710______________uni00D7Total magnification______________uni00D7______________uni00D7______________uni00D7______________uni00D7Working distance______________mm______________mm______________mm______________mmDetail observedLettereField size (diameter)_____mm_____uni03BCm_____mm_____uni03BCm_____mm_____uni03BCm_____mm_____uni03BCmFigure 3.3Relative working distances of the 10uni00D7, 45uni00D7,and 100uni00D7objectives.10×45×100×StageMARI2192_11_C03_pp027-038.indd3110/29/122:44 PM 32Exercise 33Record this figure in the appropriate space marked “field size”on the Summary Chart (page 31). (If you have been usingthe scanning lens, repeat the procedure with the low-powerobjective lens.)Complete the chart by computing the approximatediameter of the high-power and oil immersion fields.The general formula for calculating the unknown fielddiameter is:Diameter of fieldA*total magnification of fieldA=diameter of fieldB*total magnification of fieldBwhereArepresents the known or measured field andBrepre-sents the unknown field. This can be simplified toDiameter of fieldB=diameter of fieldA*total magnification of fieldAtotal magnification of fieldBFor example, if the diameter of the low-power field (fieldA) is2 mm and the total magnification is 50uni00D7, you would computethe diameter of the high-power field (fieldB) with a totalmagnification of 100uni00D7as follows:Field diameterB=(2 mm*50)/100Field diameterB=1 mm3.Estimate the length (longest dimension) of the followingmicroscopic objects.Base your calculations on the field sizesyou have determined for your microscope.Object seen in low-power field:approximate length:__________mmObject seen in high-power field:approximate length:__________mmor__________uni03BCmObject seen in oil immersion field:approximate length:__________uni03BCmThe Microscope FieldBy this time you should know that the size of the microscopefield decreases with increasing magnification. For future mi-croscope work, it will be useful to determine the diameterof each of the microscope fields. This information will al-low you to make a fairly accurate estimate of the size ofthe objects you view in any field. For example, if you havecalculated the field diameter to be 4 mm and the object beingobserved extends across half this diameter, you can estimatethat the length of the object is approximately 2 mm.Microscopic specimens are usually measured in mi-crometers and millimeters, both units of the metric system.(You can get an idea of the relationship and meaning of theseunits fromTable 3.1. A more detailed treatment appears inthe appendix.)A C T I V I T Y 3Estimating the Diameterof the Microscope Field1.Obtain a grid slide, which is a slide prepared with graphpaper ruled in millimeters. Each of the squares in the grid is1 mm on each side. Use your lowest-power objective to bringthe grid lines into focus.2.Move the slide so that one grid line touches the edge of thefield on one side, and then count the number of squares youcan see across the diameter of the field. If you can see onlypart of a square, as in the accompanying diagram, estimate thepart of a millimeter that the partial square represents. What is the diameter of field of a microscope?In early microscope objectives, the maximum usable field diameter tended to be about 18 millimeters or considerably less, but with modern plan apochromats and other specialized flat-field objectives, the maximum usable field can sometimes exceed 26 millimeters.
What is the diameter of the field of view at 40x?Stage micrometer at 1000x magnification with Olympus Compound Microscope. The diameter of field of view (fov) is 0.184 millimeters (184 micrometers).
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. What is the field diameter when using 10X objective?Your microscope has 10X oculars. The diameter of the field of view measured 2.0 mm when using the 10X objective.
What is the diameter of the field of view for this microscope on low power?Diameter of field using low power objective lens = 1.8 mm, convert to micrometers. Diameter of field using high power objective lens = 0.5 mm, convert to micrometers.
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What is the formula for calculating the diameter of an unknown microscope field?
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