Reasonable alignment of the optical microscopes objective lens and eyepiece
There are two main factors to consider when selecting objectives and eyepieces:
Class category matching. That is, all plan objectives must be used in conjunction with special plan eyepieces.
The second is the reasonable matching of magnification. Under a certain magnification, the objective lens and eyepiece can be combined arbitrarily, but the premise of the combination is mainly to consider the effective magnification, which is an important rule for the correct use of the microscope. The effective magnification of the microscope is 500-1000 times the numerical aperture of the objective lens used, that is, the product of the magnification of the objective lens and the eyepiece is equal to 500-1000 times the numerical aperture of the objective lens.
If a 40X objective with a numerical aperture of 0.65 is used to observe a specimen, what size should I choose?
First calculate the effective total multiple according to the effective magnification, and then divide by 40, which is the multiple of the eyepiece to be selected. The calculation process is: (0.65×500～0.65×1000)÷40≈8～16. That is to say: the objective lens with numerical aperture of 0.65 should match the eyepiece with 8-16 times in the range of effective magnification (500-1000 times). If the eyepiece magnification is too low, the total magnification is too small, the resolution of the objective lens cannot be fully utilized, and the identifiable details are crowded together due to the small total magnification, making it difficult to distinguish. The magnification obtained by the eyepiece higher than 16 times is called "null magnification", which does not improve the resolution of the affected details, but the depth of clarity is small and cannot clearly reflect the structure of different levels.
