Use of Bright Field Microscope

Microscopy Methods in Microbiology
Microroscopy Methods in Microbiology Part 2
Microroscopy Methods in Microbiology - Introduction
Observation of Microbes in the Living State
Observation of Microbes in Smears
Dyes and Staining
Useful pH Range and Colour Change of Some Indicator Dyes
Factors Affecting Staining
Microscopy and Micrometry
Microscopy and Micrometry - Introduction
Behaviour of Light
Light Theories
Resolving Power
Refraction and Reflection
Bright Field Microscopy
Use of Bright Field Microscope

Use of Bright Field Microscope

	Use of bright-field microscope: Research microscope is a carefully fabricated instrument with mainly four optical units namely (i) lamp, (ii) condenser, (iii) objectives and (iv) ocular. For the best performance all these should be installed in the common axis. Objectives and ocular should be fixed relative to each other. Steps necessary to follow for the effective use of microscope are as under: (1) Adjust the mirror so that light travels up the body tube of microscope.
(2), Remove the eyepiece and observe the back of the objective. Close the condenser diaphragm until its edge is just visible and centre the condenser by means of screw adjustments till iris aperture is just in the centre of the objective lens aperture. Now adjust the iris diaphragm so as to fill two third of the back aperture of objective with light. (3) Place the slide having specimen on the stage and centre the section to be examined over the centre' of stage (4) With low power objective in position, lower the body tube with the help of coarse adjustment knob until the distance between the specimen and objective becomes just about 5-7 mm.
(5) Look through eyepiece and bring the object in focus with the help of coarse adjustment knob. Do not move downwards, since you cannot see the movement of objective during focusing. (6) Sharpen the image with fine adjustment knob. Adjust the condenser and iris diaphragm to obtain good glare free view of the object. (7) If you desire higher magnification, change the objective by shifting the nosepiece in the appropriate direction till it Clicks into the place. Do not touch the lens of objective.
(8) Focus the object with the help of coarse and fine adjustment knobs. Different power objectives have different field areas and therefore, adjustment of iris diaphragm is necessary again. (9)To set up oil-immersion objective, first rack up the body tube and place a drop of immersion oil of correct refractive index (1.515) on the specimen. (10) By observing from the sides of instrument, rack the objective down to make contact with the oil and continue the same carefully till the objective lens' face is almost touching the specimen. Care should be taken-not to touch the objective with specimen and air bubble to enter in the oil.
	(11) Look through the ocular and slowly focus upwards with the fine adjustment until the image appears. This will come quickly, since the working distance of oil-immersion objective is about 0.1-0.15 mm. Sharp image can be viewed by critical focusing with fine adjustment knob and adjustment of iris-diaphragm. (12) Clean the oil from objective with lens paper immediately after the use.

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