Microscope Parts and Functions PDF

THE MICROSCOPE TOOLS OF THE BIOLOGIST New scientific instruments and techniques have allowed biologists to increase their understanding of very small objects, like cell structure and function One of the most important tools has b...

THE MICROSCOPE TOOLS OF THE BIOLOGIST New scientific instruments and techniques have allowed biologists to increase their understanding of very small objects, like cell structure and function One of the most important tools has been the microscope, which from its invention in the 1500s has completely changed the study of biology Microscope: The Tube that Changed the World THE COMPOUND LIGHT MICROSCOPE Uses two lenses: ⚫ the ocular lens ⚫ the objective lenses One lens enlarges the specimen and the second magnifies it even more Specimens are often “wet mounted” This is the kind of microscope we will be using in the lab PARTS OF THE COMPOUND LIGHT MICROSCOPE PARTS OF THE COMPOUND LIGHT MICROSCOPE 1. Ocular Lens (Eyepiece)- what you “look through” and is closest to the eye. It usually magnifies 10x 2. Body Tube- holds eyepiece lens at the top and objective lenses at the bottom, holds mirrors inside 3. Revolving Nosepiece- rotating piece that hold the objective lenses 4. Scanning Objective Lens- magnifies 4x 5. Low Power Objective Lens- magnifies 10x 6. High Power Objective Lens- magnifies 40x 7. Stage- platform that holds the specimen to be examined PARTS OF THE COMPOUND LIGHT MICROSCOPE 6. SS 8. Stage Clips- holds glass slide in place 9. Arm- holds the body tube and the base 10. Diaphragm- controls the amount of light that reaches the specimen 11. Coarse Adjustment Knob- large knob used for focusing the specimen with the low power objective lens 12. Fine Adjustment Knob- small knob used for some focusing with low power objectives and for all focusing with the high power objective 13. Light Source- reflects and focuses light on the specimen 14. Base- supports the microscope LET’S REVIEW! MAGNIFICATION To determine the total magnification of the microscope, multiply the magnification of the ocular by the magnification of the objective lens For example: Ocular = 10x Objective Lens = 40x Total Magnification = 10 X 40 = 400 One millimeter ( mm ) is equal to 1,000 micrometers (or microns). The abbreviation for micron is µm. RESOLUTION Resolution is the ability of the microscope to show two points that are close together, as separate images (just like on a TV or computer screen) Basically, it’s how sharp of an image the microscope produces The higher the resolution, the clearer the image (and the more expensive the microscope!) FIELD OF VIEW What you see when you look through the ocular As magnification increases, the size of the image increases and the field of view decreases As the power of the objective increases, the brightness of the image decreases FIELD OF VIEW: NEW YORK CITY “Low Power” (zoomed out, poor detail, can see more!) “High Power” (zoomed in, greater detail, can see less!) HOW DOES AN IMAGE LOOK UNDER THE MICROSCOPE? Because the body tube is filled with mirrors, the image is always viewed upside down and backwards e e Moving the slide to the right causes the image to move to the left (and vice versa) Moving the slide up causes the image to move down (and vice versa) RULES FOR MICROSCOPE USE 1. Always carry with two hands, one on the base and one on the arm. 2. Use lens paper to clean the lens. 3. Always remove slides before putting the microscope away. 4. View slides with the lowest power objective first. 5. Keep microscopes away from the edge of the desk. 6. Return your objective to the lowest power before you put the microscope away. 7. Never use the coarse adjustment knob while using the high-power objective. VIEWING OBJECTS UNDER THE MICROSCOPE 1. Position the specimen under the objective lens 2. Make sure the diaphragm is at its widest (allows the most light through) 3. Use the scanning lens to make sure the specimen is centered and the coarse adjustment knob to focus the image 4. Switch to low power and focus the image using the coarse adjustment first, then the fine adjustment as needed 5. Switch to high power and sharpen the image using the FINE ADJUSTMENT KNOB ONLY Preparation of a Wet Mount Slide Most of the slides we will make are wet ________ mountslides. Wet mount slides are used to view ______________, living organisms as well as _____ liquid substances of all kinds. They are also used for any sort of specimen that moist needs to be kept _____.  Preparation of a Wet Mount Slide 1. Obtain a _____________. clean, dry slide 2. Put your _________ specimen in the center of the slide. 3. Add one large drop of ______. water (It should be one solid drop of water over the specimen.) It should not… ….run all over the slide or get on the back of the slide. 4. Hold a clean coverslip _______ 5. Gently drop the coverslip into at a ________ 45-degree angle place. over the specimen. 6. The whole coverslip should Allow one edge of the be in contact with water, but coverslip to touch the make sure the back of the edge of the drop of slide is dry. water. MICROSCOPIC MEASUREMENTS In this class we will be using a compound light microscope to view tiny specimens and cells The unit of measurement used to measure tiny objects is the micrometer (µm) One meter = 1000 millimeters (mm) 1 millimeter = 1000 micrometers! Another (shorter) name for micrometers is “micron” CONVERTING BETWEEN MILLIMETERS AND MICROMETERS 1 millimeter = 1000 micrometers To convert millimeters to micrometers, move the decimal point 3 places to the right Example: ⚫ 5.0 mm = 5000. _____ µm “Milli to mic, 3 to the right!” YOU TRY IT! 1. 3.2 mm = 3200 ____. µm 400. 2. 0.4 mm = ____ µm 10. 3. 0.01 mm = _____ µm.500 4. 500 µm = _____ mm.045 5. 45 µm = _____ mm  How to Determine the Field of View The field of view or FOV is the diameter of the circle of light that is visible when looking into the microscope. 0 1 2 3 4 5 6 7 8 If you put a clear ruler under the low or medium power objective lens of a microscope, you can measure the FOV. ESTIMATING SIZE The size of whatever object you are measuring can be determined by finding the distance of the diameter of the field of view, and dividing it by the number of objects that could fit across it: An object viewed under a microscope actual size = field of view diameter of lens being used ——————————————————————— estimated number of objects that fit across field of view EXAMPLE #1: Estimate the length of each plant cell (in both mm and µm) based on the given diameter of the field of view. Cell Size = 3.0 mm 5 cells Cell Size = 0.6 mm 0.6 mm = 600. µm 3.0 mm EXAMPLE #2: Estimate the length of the paramecium (in both mm and µm) based on the given diameter of the field of view. Cell Size = 0.6 mm 3 cells Cell Size = 0.2 mm 0.2 mm = 200. µm 0.6 mm DETERMINING FIELD OF VIEW DIAMETER UNDER HIGH POWER It is impossible to physically measure the diameter of the high power field if view using a ruler. Why is this? Instead, we need to use an equation to convert the field of view measurements from the lower power using an equation like this: low power magnification x —————————— = —————————— high power magnification low power FOV diameter EXAMPLE #3 What is the field diameter (in mm) under high power (400x) if the field diameter under low power (100x) is 3mm? 100 = ___n___ Can you convert that to µm? 400 3.0 mm 400(n) = 3.0 mm (100) 0.75 mm = 750 µm 400(n) = 300 n = 300/400 n = 0.75 mm EXAMPLE #4 What is the field diameter under high power (400x) if the field diameter under low power (100x) is 500 µm? 100 = ___n___ 400 500 µm 400(n) = 500 µm (100) 400(n) = 50000 n = 50000/400 n = 125 µm EXAMPLE #5: PUTTING IT ALL TOGETHER The following image are plant cells as seen under the high power field of view (400x). If the diameter of the low power (100x) field of view is 2.0 mm, what is the estimated size of one plant cell (in µm)? Step 1: Determine the Step 2: Determine the high power diameter: cell size diameter: 100 = ___n___ Cell Size = 0.5 mm 400 2.0 mm 5 cells 400(n) = 2.0 mm (100) Cell Size = 0.1 mm 400(n) = 200 Step 3: Convert to µm n = 200/400 0.1 mm = 100 µm n = 0.5 mm