Proper Microscope Usage for Students. Learn how to use proper light, focus at right amount, and also diagraphm settings.
Proper Microscope Usage for Students
While it may seem not worth mentioning, it is surprising to learn that a great many people do not know how to focus a microscope. The author has seen many students look through the tube and focus down on the subject. This is reprehensible. Never do it, for sooner or later you are going to run the objective down too far and break the cover glass and possibly ruin the slide, or you may break the objective, which would be even more regrettable. The proper way to bring an object into focus is to focus up on it. To do this, look at the objective from the outside, at the same time lowering the tube toward the specimen until you are sure it is closer than is necessary to secure sharp focus. Then look into the tube and draw the lens away from the subject until it is in focus. A good rule to remember is this: always move the tube down when you are looking at it and up when you are looking through it. If the microscope is equipped with both coarse and fine adjustments the tube may be lowered with the coarse adjustment knob, then roughly focused by raising the tube and finally getting critical focus with the fine adjustment. Never try to examine an object that is not in perfect focus, for this causes eye strain. Be sure the focus is the best possible by making slight adjustments with the fine adjustment knob. Run the tube down a little distance and if the image appears to be improved the first focus was not correct. If there is no apparent change in appearance the focus was probably just about right and so should be restored. Another error of many students is the use of too much light. More detail can be seen when the field is moderately lighted than when the eye is blinded by a dazzling glare. Just as the strong sun has a blinding effect when we look into it, so the light projected through the microscope affects the eye. Too much light is objectionable because it may lead to serious eye injury. On the other hand, do not go to the other extreme and try to work with not enough light, for this is just as bad, since we are forcing the eyes to work in semi-darkness. Keep the field sufficiently lighted to be pleasant to the sight and no injurious results will be felt. If your microscope is fitted with a diaphragm, stop this down until there is just enough light to see the object clearly. If the object is thick or opaque, more light will be needed, in which case open the diaphragm. If this accessory is not available, as in the smaller microscopes, reduce the intensity of the light by tilting the mirror, or by moving the illuminator away from the microscope, by placing sheets of tissue paper in the light path or by reducing the size of bulb used.
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