What is the formula for the micrometer in the eyepiece of a biological microscope?
When using a biological microscope, it is sometimes necessary to measure the length of the object being observed. Since the object being observed is very small, it is impossible to measure it directly with conventional measuring tools. This is why we need to use a microscope-specific micrometer. To measure the length of the object to be inspected, two tools are needed. One of them is installed in the eyepiece and is called an eyepiece micrometer; the other is placed on the stage and is a special cover glass that can be seen There is a small circular area in the middle with small scales engraved in it. The general total length is 1mm and there are 100 small grids in total, that is, the distance between each small grid is 10um. Its function is to determine the eyepiece. The length represented by each division of a micrometer under a biological microscope.
When using it, we need to install the eyepiece micrometer into the eyepiece tube first. The specific operation is: first pull the eyepiece out of the microscope. There is a gear-shaped end at the end away from the lens (that is, where we usually look when observing). The circular structure, unscrew it, and then install the eyepiece micrometer into it. Make sure the front side is placed on the field diaphragm, then screw it back and put it back into the eyepiece. Some microscopes are not allowed to be disassembled due to their precise structure, and must be equipped with micrometer eyepieces. Then place the micrometer scale on the stage and adjust the focus of the microscope until you can see the clear scale of the scale. At this time, adjust so that one end of the two rulers overlaps at the full scale, and then find where the other end overlaps. By counting the number of grids in their overlapping parts, you can calculate the actual magnification of the eyepiece micrometer under magnification.
The specific calculation formula is as follows:
Each grid of the eyepiece micrometer = (number of overlapping grids on the bench ruler X 10) ÷ number of overlapping grids on the eyepiece micrometer. As shown in the figure above, the number of overlapping grids on the table ruler is 4, and the number of overlapping grids on the eyepiece micrometer is 10. From this, we can calculate that the length represented by each division of the eyepiece micrometer is: (4X10)/10=4um.
After determining the length represented by each division of the eyepiece micrometer, remove the ruler. You can use it to determine the actual length of the object being inspected later. Since a biological microscope has multiple objective lenses, each objective lens has a different magnification, and the eyepiece micrometer represents different actual lengths at different magnifications, so it should be recalibrated when switching magnifications.
