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Benet Academy S-211 Bro. Guy, OSB 2010-11 Microscopes and their Use Many of the structures and organisms that you are going to examine in Biology are so small that you cannot see the pertinent details without the aid of some magnifying device. A simple biconvex lens would be adequate for furnishing a magnification of 4 to 6 times (x). For magnification higher than these, however, a microscope using several separate lenses must be used. A. Care of Microscopes Since the microscope is a relatively expensive piece of equipment for which you are being held responsible, you should be aware of certain standard precautions before handling your microscope. 1. A microscope should always be treated with care due an expensive and delicate piece of equipment. a. The lenses must NEVER be touched with anything except LENS PAPER. b. The lenses should be cleaned whenever dirt spots appear in the FIELD OF VIEW. First blow on the glass to remove the dust particles and then WIPE GENTLY with lens paper. DO NOT SCRATCH THE LENSES. c. The rest of the scope (other than the lenses) should be wiped with a soft cloth. 2. ALWAYS CARRY A MICROSCOPE WITH TWO HANDS, grasping the arm with your right hand while supporting the base with your left (or vice versa). 3. NEVER remove a lens from the body tube or NOSE of the scope. 4. Be careful when taking the scope out of and returning it to the storage cabinet. DON’T BOUNCE OR JAR IT! B. Binocular Dissecting Microscope This microscope combines lower magnifications with binocular viewing and is of considerable value in making delicate dissections of small specimens. Use similar precautions when operating this instrument as you would for the compound microscope. C. Using the Compound Microscope Take the compound microscope from the cabinet and follow these steps: 1. Place the microscope before you in an upright position with the ARM toward you. 2. Check the lenses foe cleanliness. REMEMBER, USE ONLY LENS PAPER. 3. Place the prepared SLIDE to be studied on the STAGE in such a way that the part to be observed is centered over the hole in the STAGE. 4. Place the STAGE CLIPS over the ends of the slide in such a manner that the slide will be held securely in place. 5. Adjust the LIGHT so that the study specimen is evenly illuminated. Use the DIAPHRAGM as necessary to regulate light. 6. Avoid using too much light. With the dissecting scope, however, it is almost impossible to get too much light. 7. NEVER SQUINT. Try to keep both eyes open. 8. Try to use your left (right) eye in the monocular scope. This leaves your other eye for your drawings and you will be able to look and draw at the same time (with practice). 9. If you wear glasses, you will find that you will have less field of view than if you do not wear them. 10. An experienced microscopist ALWAYS: a. keeps both eyes open. b. checks immediately to see which OBJECTIVE LENS is being used, and, c. CONSTANTLY moves the FINE ADJUSTMENT to see depth when using HIGH POWER. 11. Steps in FOCUSING the compound microscope: a. Rack up with COARSE ADJUSTMENT. b. Place slide over the opening in the stage and position the stage clips. c. TURN YOUR HEAD TO THE SIDE AND CHECK TO MAKE CERTAIN THAT the low power objective IS IN PLACE. d. Rack the coarse adjustment all the way down while WATCHING FROM THE SIDE TO BE SURE THAT THE OBJECTIVE DOES NOT HIT THE SLIDE. e. Look into the OCULAR and rack slowly upward until the object is visible. Then use the FINE ADJUSTMENT to clear up the focus. f. And (AND NOW ONLY) the HIGH POWER OBJECTIVE may be swung into position. Watch as you do this to make sure there is clearance. Then you MUSE USE THE FINE ADJUSTMENT KNOB ONLY. NOTE: A compound microscope is NEVER RACKED DOWN ON HIGH POWER> The high power lens is never used until the scope is first focused on low power. 12. “Put-away” steps for the compound microscope. a. Remove slide. b. Place low power objective in place. c. Rack all the way down. d. Put DUST COVER on the scope and return it to the cabinet, being careful NOT to bump the ocular on the edge of the cabinet, or jar the instrument when setting it down. REMEMBER: You are responsible for learning the parts of the compound and dissecting microscopes (or reviewing them). Consult your texts, available software, web sites, other reference works, your teacher, and the Library for additional help.
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