The use of microscope oil immersion system
Experiment summary
Correctly master the method of using and caring for the microscope, especially the use and care of the oil immersion system.
Experimental principle
Ordinary optical microscopes include two parts, the mechanical part and the optical part. The mechanical part includes mirror base, mirror arm, mirror tube, stage, objective lens converter, coarse adjustment screw, fine adjustment screw, specimen holder, etc. The optical part includes eyepiece, objective lens, mirror, aperture (rainbow), condenser lens (collector), etc.
The immersion system is to add 1 drop of cedar oil between the oil immersion mirror and the specimen, and adjust the light source to check the bacterial specimen. Oil immersion mirror is a high-magnification objective lens, generally engraved with magnification, such as 95x, 100x, etc. Its lens marks are mostly represented by the word "oil" for domestic lenses, while foreign products are represented by "Oil" (Oil Immersion) or HI (homogeneous Immersion). Moreover, the lens body of the oil lens is longer than the higher magnification lens and the lower magnification lens, and the lens is the smallest, which is another sign of identification. The principle of its use is: because the refractive index of cedar oil and glass is similar (1.515 for cedar oil and 1.52 for glass). During microscopic examination, the effect of adding cedar oil
It is to make the light source enter the objective lens as much as possible to avoid the loss of light through the air with a low refractive index (refractive index 1.0), thus improving the resolution of the objective lens and making the object image bright and clear.
Experimental procedure
1. The examiner needs to have a correct posture. Generally, the left eye is used for observation, and the right eye is used for drawing and recording. Both eyes are opened at the same time to reduce fatigue. The light source uses natural light or artificial light source, pay attention to avoid direct sunlight. When using an artificial light source, in order to avoid reddish-yellow light, a blue filter needs to be installed under the collector lens.
2. Fully open the aperture to the light, raise the condenser to the same height as the stage, place the specimen on the stage, face the light under a low-magnification lens, and adjust it by turning the reflector by hand until the field of view is brightest. If a natural light source is used, it is advisable to use a reflector plane, and a weaker light source should use a concave surface. When inspecting unstained specimens, the light should not be too strong, and strong light is required for stained specimens. The intensity of the light can be adjusted by enlarging or narrowing the aperture, lifting the condenser, and rotating the mirror.
3. Add oil and put the specimen on the stage, with the dyed part facing the center of the light collector, fix it with a specimen clip, add 1 drop of cedar oil, check with an oil immersion mirror, make the oil lens immerse in the oil drop, almost contact with the specimen surface, then look into the mirror from the eyepiece, and at the same time slowly turn the coarse adjustment screw to lift the lens barrel (never lower the lens barrel!) until the object image can be seen blurred, then turn the fine screw (the fine screw generally does not rotate more than one circle) until the object image is clear.
Precautions
1. When taking the microscope out of the mirror box, hold the mirror arm with the right hand and pull it out slowly in the horizontal direction without touching the mirror, and then hold the mirror base with the left hand to keep the mirror body parallel to prevent the mirror and eyepiece from slipping off.
2. The lenses of the microscope must never be wiped with fingers, and should be wiped lightly with lens cleaning paper or silk cloth. After the oil lens is used, wipe it with lens tissue immediately. If the oil stain is dry, wipe it with lens tissue dipped in xylene, and then wipe it lightly with dry lens tissue. The mirror body can be wiped with a soft cloth to keep it clean.
3. After use, all parts of the microscope should be reset, especially pay attention not to let the objective lens face the light collector, and at the same time lower the light collector to avoid collision, and then put it in the mirror box and lock it.
4. Pay attention to moisture-proof, keep away from heat source and corrosive chemicals. Do not disassemble any parts of the microscope, especially the optical part, to avoid damage.
