When you zoom in 400 times (10x, 40x), you can hardly see the bacteria, but it is only the size of a needle tip, just like a dot. Generally, we still zoom in to 1000 times (10x, 100x) for observation. At this point, the appearance of bacteria can still be clearly seen, even after special dyeing flagella. An oil mirror is needed to enlarge 1000 times. The so-called oil mirror is to drop a drop of aromatic tar between the objective lens and the cover glass. The light refractive index of aromatic tar is higher than that of air, so a larger magnification can be used.

10x and 40x indicate that this lens is enlarged by 10x and 40x. Multiply the magnification of the eyepiece by the magnification of the objective lens to get the total magnification of this microscope. The eyepiece and objective lens of the microscope used in middle school can be changed. General eyepiece is 5x, 10x. Generally, the higher-level microscope eyepiece is only 10x. We are now using Olympus and Leica microscopes, and we have seen Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Bacillus megaterium (used to see spores).