Encyclopedia of Ayurvedic Medicinal Plants

PERIPHERAL-BLOOD-SMEAR-DEMONSTRATION- instructions

             The illumination system include the light source in the base of the microscope and condenser with iris diaphragm. The iris diaphragm is placed below the condenser and is used to control the amount of light entering the microscope. It can be closed or opened by means of a lever. C. Image formation The microscope can be considered to be composed of two simple convex lenses,i.e, the objective lens and eye piece lens.

         The objective lens forms a real and inverted magnified image of the object. The eye piece lens further magnifies the image so that a virtual magnified image of the object is formed. D. Magnification by the microscope Magnification produced by the microscope is equal to objective magnification multiplied by eye piece magnification. Thus a low power objective of 10 and an eye piece of 10, the total magnifications is 10X10 = 100 times. High power objective with magnification 45x gives a total magnification of 45 x 10 = 450 times. Oil immersion objective of magnification 100 produces a total magnification of 100x100 = 1000 times. E. Adjustments of the microscope

              1. Low power: The low power objective (10 x) is brought in line with the eye piece lens. The body tube is raised, condenser is lowered, iris diaphragm half opened, concave mirror is turned towards the source of light. Looking through the side, lower the objective as much as possible. Then looking through the eye piece raise the body tube till a clear view is obtained. 2. High power: High power objective is brought in position. The body tube is raised condenser is raised, iris diaphragm is 3/4 th opened, plain mirror is turned towards the source of light. Looking through the side, lower the body tube. Looking through the eye piece, raise the body tube slowly till the image bcomes clear. 3. Oil immersion: The oil immersion objective is brought in position. Condenser is raised and iris diaphragm fully opened, plane mirror is turned towards the source of light. Focus the require area under low power. Put a drop of cedar wood oil on the slide. Looking through the sides bring down the oil immersion objective till it touches the oil. Now looking through the eye piece raise the body tube slowly till a clear image is obtained. F. OPERATING PROCEDURE This procedure explains how to use your self illuminating compound Microscope, it does not include information on general techniques of microscopy. 1. Make sure all the exposed optical surfaces are free of dirt. Plug the power cord into a gounded outlet and switch on the power. 2. Adjust the observation tube in convenient working position. 3. Rotate the nosepiece until the lowest power objective is in the viewing position. The lower the power of the objective, the greater the area of the specimen surface included in the field of view. Low power objectives also have a much greater depth of focus and are generally used for initial focussing and viewing. 4. Take down the stage to fairly low position with the help of coarse focus knob.

               5. Make sure that the stage surface is free of dust, grit or any other material that will interfere with the movement of the specimen slide across the surface of the stage or scratch the slide and the stage. Position the specimen area of the slide ( cover glass upward ) over the centre of stage aperture. Use the stage control knobs to move the specimen slide to the desired position. 6. Looking through the Observation Tube, raise the stage by adjusting the coarse focus knob until an image appears. Focus as sharply as possible with coarse focus knob. 7. Adjust the fine focus knob to sharpen the image in the centre of the field of view. 8. Look at the image and adjust the condenser aperture to obtain the sharpest possible image. The clarity of the image depends upon the size of the aperture. As the aperture becomes smaller, the contrast and the depth of focus increases, but the resolving power decreases. The clearest image is produced by the combination of these three factors. 9. Examine the specimen. When you find a feature you wish to observe at a higher magnification, move the slide so that the feature gets centered in the field of view. 10. Use the fine focus knob to sharpen the image. Until you gain sufficient experience in use of this microscope, it is advisable to always obtain an image and to do the focusing with lowest power objective and then to increase magnification by going to successively higher power objectives one step at a time.

          11. When using objective of higher numerical aperture (N.A.) proper focussing of the condenser is important. Focus the condenser by racking the condenser movement knob up and down so that the field is evenly illumi- nated. 12. The procedure for examining a specimen using the 100x oil immersion objectives is as follows: 1. Rotate the nosepiece so the lowest power objective is in the light path. 2. Place one drop of immersion oil on the lighted area of the specimen slide. Dust or air bubbles in the oil can destroy the definition of the image. If the bubbles are trapped between the objective lens and the slide, clean off the oil and start again. Keep the oil tightly stoppered and don ’ t shake the bottle. 3. Rotate the nosepiece so that the 100x oil immersion objective is in the light path. 4. With your eye at the level of the stage, use coarse focus knob to raise the stage with specimen cover glass. When you see a flash of light at this location, the objective lens has made contact with the immersion oil and the microscope can be focused using the fine focus knob. 5. Each time you finish using the oil immersion objective, wipe off all traces of oil from the objective and the specimen cover glass with a lens tissue or clean soft cloth. Care of the Microscope: 1. Do not touch the lens with the hand. 2. Keep the Microscope protected from moisture and direct sun light. 3. After using oil immesion, clean the objective lens and slide using the tissue paper. Questions: In a tabular form, compare the adjustments for Low power, High-power, and Oil immersion? Why is Cedar wood oil used in oil immersion view