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Compound Light Microscopes Magnification

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Compound Light Microscopes Magnification Compound Light Microscopes • Frequently used tools of biologists. • Magnify organisms too small to be seen with the unaided eye. • To use: – Sandwich specimen between transparent slide and thin, transparent coverslip. – Shine light through specimen into lenses of microscope. • Lens closest to object is objective lens. • Lens closest to your eye is the ocular lens. • The image viewed through a compound light microscope is formed by the projection of light through a mounted specimen on a slide. Eyepiece/ ocular lens Magnification Nosepiece Arm Objectives/ • Magnification - the process of objective lens enlarging something in appearance, not Stage Clips Light intensity knob actual physical size. Stage Coarse DiaphragmDiaphragm Adjustment Fine Adjustment Light Positioning knobs Source Base Always carry a microscope with one hand holding the arm and one hand under the base. What’s my power? Comparing Powers of Magnification To calculate the power of magnification or total magnification, multiply the power of the ocular lens by the We can see better details with higher power of the objective. the powers of magnification, but we cannot see as much of the image. Which of these images would be viewed at a higher power of magnification? 1 Resolution Limit of resolution • Resolution - the shortest distance • As magnifying power increases, we see between two points more detail. on a specimen that • There is a point where we can see no can still be more detail is the limit of resolution. distinguished as – Beyond the limit of resolution, objects get two points. blurry and detail is lost. – Use electron microscopes to reveal detail beyond the limit of resolution of a compound light microscope! Proper handling technique Field of view 1. Carry microscopes with one hand on the • Field of view - the diameter of the circle arm and one of view when you look down the supporting the base. microscope. 2. Carry microscopes vertically. 3. Use proper focusing techniques at all times! What happens to the size of the field of view as you increase magnification? Proper focusing technique Proper clean up technique 1. Check the lighting – be sure the voltage dial is set at max. 2. Place the slide on the stage, centering the specimen over the opening in the stage. 1. Clean up right away 3. Keep the eye open that is not looking through the 2. Go back to low power eyepiece. 4. WITHOUT looking through the scope, move the 3. Lower the stage stage using the coarse focus knob to bring the low power objective as close to the slide as possible. 4. Remove the slide 5. Look through the eyepiece and use the coarse focus knob to FOCUS DOWN until the specimen 5. Proper storage is in focus. 1. Check the stage 6. Use the fine focus knob to perfect the image. 7. NEVER use the coarse focus knob from this point 2. Check the objective on! 3. Wind the cord 8. Move the nosepiece to medium power. Use the fine focus knob to perfect the image. 4. Dust cover it 9. Move the nosepiece to high power – if you are focused properly, you will not hit the slide! Use the fine focus knob to perfect the image. 2 How to make a wet-mount slide … Proper storage technique 1 – Get a clean slide and coverslip. 2 – Place ONE drop of water or stain in the middle of the 1. The stage must be all slide. Don’t use too much or the liquid will run off the edge! the way down. Place the specimen in the drop. 2. The low power 3 – Place the edge of the cover slip on one side of the water objective must be in drop. place. 4 - Slowly lower the cover slip on top of the drop with fingers Cover 3. The slide must be or forceps. Lower slowly removed. Slip 4. The cord must be wound around the 5 – Remove bubbles by tapping. Dry the bottom and sides of base. the slide. 5. The dust cover must 6 - Place the slide on the stage and view it first with the low be replaced. power objective. Wash and dry the coverslip and slide when finished. 3.
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