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Observing in Biology Index
WORKING IN THE LABORATORY
Looking at the slide using the microscope
Follow these instructions every time that you use a microscope and you will not have any problems in using it. It takes a bit of practice, however, so do not give up; call for help if you have difficulty.
Take the microscope from its cupboard. Be careful; it is heavy. Use bout hands to carry it to your place. Keep it upright all the time.
Put the microscope gently on the bench and plug in the lamp on the bottom. Now turn the microscope and lamp so that the objective lenses are facing away from you.
Make sure that the low power objective lens is clicked into place on the rotating nose piece.
Put the slide and object on the stage of the microscope and hold the slide in place using the spring clips.
Lower the microscope using the coarse focusing knob as low as it can go without touching the slide. You must look from the side of the microscope when you do this.
Now look down the eye-piece lens. Adjust the light using the diaphragm. The diaphragm opens and closes a hole which lets more or less light into the microscope. On low power you will need less light. Close the diaphragm until you see things more clearly. If you leave it right open you will soon get a headache!
Focus the microscope by turning the coarse focusing knob, slowly, as you are looking down the eye-piece. When you look down the eyepiece you will see the object in a circle of light. This is called the field of view and the specimen that you are looking at should be right in the middle of it. The specimen that you are looking at will become clear but it may not be right in the centre; you will have to move the slide.
Now you will find something strange. When you move the slide to the left the specimen appears to move to the right in the eye-piece. When you move the slide to the right the specimen appears to move to the left. Now try moving the slide towards you and away from you. You will get used to this but it is confusing at first.
You can now turn the rotating nose-piece to the medium power objective lens. Make sure that the lens clicks into place.
You will need to refocus a bit using the coarse focusing knob and you will have to increase the light by opening the diaphragm. You will also find that the object is bigger but not in the centre of the field of view. Move the slide to centre the object.
For really small specimens you will need to turn to the high power objective lens. This needs some practice. Everything will be magnified 400 times or more, so when you move the slide a fraction of a millimetre it is magnified 400 times!
Before you turn to the high power lens make sure that the specimen is right in the centre of your field of view. Turn the rotating nose-piece again so that the high power lens clicks into place. Be careful; the lens will be very close to the slide this time. Refocus again using the fine focusing knob. You will need more light so open the diaphragm some more.
Taking care of your microscope
It is very easy to get finger marks on the eyepiece lens and water on the high power objective lens. The lenses of the microscope need to be kept clean so that you can see clearly. Do not use a paper towel or a handkerchief. Use the special lens cleaning tissue which is soft and will not damage the lenses.
Sometimes water spills onto the stage where the slide is held. You should wipe this dry. You can use paper towel for this.
Putting the microscope away
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