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Microscope Use Exps

Microscope Use: In school labs simple compound light microscopes (electron microscopes for greater resolution) are used to observe specimens. These microscopes usually have an eyepiece lens with 10X magnification and three objective lenses of 4X, 10X and 40X magnification. Total magnification is found by multiplying the power of the eyepiece lens by the objective lens e.g. 10X x 40X = 400X magnification Real size= (apparent size)/magnification e.g. 0.8/400=0.002mm The fine and course focus wheels are used to make adjustments to the stage to bring the specimen into focus under low and medium power, only the fine focus is used at high power. Coarse focus wheel is for large adjustment and the fine focus wheel is for smaller adjustments. Preparing a plant cell for observation: An onion is cut into small pieces (using a knife with cuts away from the body) and then a thin piece of onion is removed using forceps and it is placed on a slide. A coverslip is added to protect the objective lens and prevent sample drying out. Coverslip is added at an angle of 45 degrees using a forceps (to ensure there are no air bubbles). Light level is controlled by adjusting the diaphragm. Under low power the coarse and fine focus wheels are turned to bring the cell into focus. Then at high power the fine focus wheel is used to focus the image. Iodine is added to stain nucleus, chloroplasts and cytoplasm and the cell is sketched Preparing an animal cell for observation: A cotton ear bud is rubbed on the inside of the cheek to remove some cells which are then spread on a slide. A coverslip is added to protect the objective lens and prevent sample drying out. Coverslip is added at an angle of 45 degrees using a forceps (to ensure there are no air bubbles). Light level is controlled by adjusting the diaphragm. Under low power the coarse and fine focus wheels are turned to bring the cell into focus. Then at high power the fine focus wheel is used to focus the image. Methylene Blue is added to stain nucleus and cytoplasm and the cell is sketched.