What is the principle of the oil mirror in an optical microscope?
Oil microscope, one of the optical microscopes, when used, the lens is immersed in oil (usually cedar oil), used to observe the finer structures, is one of the commonly used microscopes in the laboratory, the clarity is slightly higher than the ordinary optical microscopes, used to observe chlamydia, bacteria, organelles and so on. The lens of the oil lens is very small, and the light passes between the slide and the oil lens...
A microscope with a magnification of 100x is an oil lens, which requires a drop of cedar oil on the slide in order to see the object under the lens clearly.
The reason why you need to add cedar oil to the slide when using an oil mirror. This is because the magnification of the oil mirror is high, and the lens is very small, the light through the different densities of the medium object (slide → air → lens), part of the light will be refracted and scattered, into the lens barrel of the light is less, the field of view is darker, the object is not clearly observed. Such as between the lens and the slide drop and glass refractive index (n = 1.52) similar to the cedar oil (n = 1.515), the light into the oil mirror increases, the field of view brightness enhancement, object clarity.
Microorganisms are generally smaller and are observed more clearly with oil microscopy at a higher magnification!
Simply put, the refractive index of cedar oil is smaller than the refractive index of air, and the light passing through the small cells will enter the objective lens more, and then easier to observe.
How to use the oil immersion objective of a light microscope.
When using an oil immersion objective, generally do not use the same height focusing. Same-height focusing is only applicable to the original objective lens of each microscope, and it is an extremely favorable and convenient condition when using low and high magnification objectives, but when using oil immersion objectives, it is subject to certain limitations. Generally speaking, when observing the specimen slice without coverslip (slide) with an oil microscope, it is more safe to use the same-height focusing, whereas for the specimen slice with a coverslip, it should be used carefully because the working distance of the oil immersion objective lens is very The isoheight considered in the design and assembly is for standard thickness coverslips.
When using an oil-immersion objective, apply only a drop of cedar oil to the specimen sheet. After observation, cleaning work should be carried out in time, if not carried out in time, the cedar oil sticks to the dust, dust particles may wear the lens when wiping, cedar oil in the air exposed for a long time, it will also thicken and dry, wiping is very difficult, and is very unfavorable to the instrument. Wiping should be done carefully and gently. Oil-immersed objective lens front end first with a dry wiping paper once or twice, to remove most of the oil, and then use xylene drops wet wiping paper to wipe twice, and finally dry wiping paper to wipe once. Specimen piece of cedar oil can be used to "pull the paper method" (that is, a small piece of microscope paper covered in cedar oil, and then drop some xylene on the paper, while wet to pull the paper outward, so that three or four times in a row, can be clean, generally will not be damaged by the smear specimens without coverslips) to wipe clean. Mirror paper should also be dustproof, generally before use, each page will be cut into 8 small pieces, stored in a small clean petri dish, with both savings and convenience.
