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Parts of the Compound Light Microscope. BY: MARY GRACE L. VEGA. Microscope. One of the most important tools used to study living things. “Micro” means very small “Scope” means to look at. Diagram of a typical student light microscope, showing the parts and the light path.
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Parts of the Compound Light Microscope BY: MARY GRACE L. VEGA
Microscope One of the most important tools used to study living things. “Micro” means very small “Scope” means to look at Diagram of a typical student light microscope, showing the parts and the light path
Test Your Knowledge#1 The word “microscope” means: A. Glass eye B. Small ~ to look at C. To search for
You are Correct! The word “microscope” means VERY SMALL ~ TO LOOK AT
Parts of the Compound Light Microscope • Mechanical parts- used to support and adjust the parts
Mechanical parts • Arm/ neck • Stage • Stage clip • Body tube • Draw tube • Revolving/rotating nosepiece • Dust shield-lies atop the nosepiece and keeps dust settling on the objectives • Coarse adjustment knob • Fine adjustment knob
Illuminating Parts • Mirror/illuminator • Electric lamp
Magnifying Parts • Ocular/ eyepiece • Objectives -LPO -HPO -OIO
A B M C L K J D I E H F G Slide # 2 Microscope Parts and Functions B. Arm: supports tube & connects it to the base C. Stage Clip: holds microscope slide in place D. Coarse adjustment: raises / lowers stage to bring image into focus E. Fine adjustment: brings image into sharp focus F. Base: Supports microscope G.Illuminator: Light source A. Eyepiece: Holds ocular lens; lens that you look through; magnified image of objective lens
Slide # 3 A B M C L K J D I E H F G Microscope Parts and Functions I.Stage: platform that holds the slide J. Microscope slide: holds the specimen K. Objective lenses: magnifies the specimen • Shortest lens has least magnification • Longest lens has greatest magnification H. Diaphragm: Controls the amount of light that passes through a specimen
A B M C L K J D I E H F G Microscope Parts and Functions Slide # 4 L. Revolving /rotating nosepiece: rotating disc where the objectives areattached M. Body tube: Connects eyepiece to objective lens
Slide # 5 How to Calculate Magnification If eyepiece is 10 x and objective lens is 4x, then what is the total magnification? Magnification of eyepiece X magnification of objective lens 10x X 4x = 40X
Slide # 6 TAKS PRACTICE A 4X B 10X C 40X D 100X How do we calculate magnification? Eyepiece X Objective lens = Total magnification A student wants to view cells under the compound microscope at a total magnification of 400X. If the eyepiece is 10X, which of the following objective lenses should be used? Correct Answer = C 10x X n = 400x 10x = 10x n = 40x
Slide # 7 How a Light Microscope Works • Use lenses to make small objects appear larger • Compound light microscope: Two lenses separated by a tube • Lenses magnify an object by bending the light that passes through the lens • Magnification: ability to make things appear larger than they are • Resolution: fineness of detail that can be seen in an image Go to Section:
Slide # 8 Microscope Safety 1. Always use 2 hands to carry a microscope; one on the arm and one hand supporting the base 2. Only use lens tissue to clean lenses 3. When focusing, always look to the side to watch andmake sure the objective lens doesn’t hit the slide 4. Always use the lowest power (shortest) objective lens for bringing specimen into focus • Bring specimen into focus by first using coarse adjustment, then use fine adjustment • Because we have running water in our lab area, NEVER turn on the water when using a microscope
Focusing Specimens • Place the slide on the microscope stage, with the specimen directly over the center of the glass circle on the stage ( directly over the light). • If you wear glasses, take them off; if you see only your eyelashes, move closer. • If you see a dark line that goes way across the field of view, try turning the eyepiece.
Focusing Specimens • Use only the Fine adjustment knob when using the HIGH(long) POWEROBJECTIVE. • As much as possible, keep both eyes open to reduce eyestrain. Keep eye slightly above the eyepiece to reduce eyelash interference.
Focusing Specimens • If and ONLY if, you are on LOW POWER, lower the objective lens to the lowest point, then focus using first the coarse knob, then the fine focus knob. • Adjust the diaphragm as you look through the eyepiece, and you will see that MORE detail is visible when you allow in LESS light! • Too much light will give the specimen a washed-out appearance.
Focusing Specimens • Once you have it on High Power remember that you only use the fine focus knob! • The High Power Objective ( 40x) is very close to the slide. Use of the coarse focus knob will scratch the lens, and crack the slide.
Slide # 9 How to Prepare a Slide 1. Place slide on a flat surface. 2. Place a drop of water on the slide. Add the specimen to the drop of water (at times, you may want to have the specimen already on the slide before adding the water). 3. Hold the coverslip by its sides and lay its bottom edge on the slide close to the specimen. Holding the coverslip at a 45° angle helps. 4. Slowly lower the coverslip so that it spreads the water out. If you get air bubbles (looking like little black doughnuts), gently press on the coverslip to move them to the edge. If there are dry areas under the coverslip, add a little more water at the edge of the coverslip. Too much water can be dabbed off with a piece of paper towel
Slide # 9 How to Prepare a Slide The diagram below shows how a cover-slip should be lowered onto some single-celled organisms during the preparation of a wet mount. Why is this a preferred procedure? A The cover-slip will prevent the slide from breaking. B The organisms will be more evenly distributed. C The possibility of breaking the cover-slip is reduced. D The possibility of trapping air bubbles is reduced.
Staining • A technique in microscopy that is used to enhance the image of the specimen. • To distinguish structures in cells and tissues.
How to stain a slide • Place one drop of stain on one edge of the coverslip, and the flat edge of a piece of paper towel on the other edge of the coverslip. The paper towel will draw the water out from under the coverslip, and the cohesion of the water will draw the stain under the coverslip.
How to stain a slide • As soon as the stain has covered the area containing the specimen you are finished. The stain does not need to be under the entire coverslip. If the stain does not cover the area needed, get a new piece of paper towel and add more stain until it does.
How to stain a slide • Be sure to wipe off the excess stain with a paper towel, so you don’t end up staining the objective lenses. • You are now ready to place the slide on the microscope stage. Be sure to follow all the instructions as to how to use the microscope.
How to stain a slide • When you have completed your drawings, be sure to wash and dry both the slide and the coverslip and return them to the correct places!
Drawing Specimens • Use pencil- you can erase and shade areas. • All drawings should include clear and proper labels ( and be large enough to view details). Drawing should be labelled with the specimen name and magnification.
Drawing Specimens • Labels should be written on the outside of the circle. The circle indicates the viewing field as seen through the eyepiece, specimens should be drawn to scale , e.g. if your specimen takes up the whole viewing field, make sure your drawing reflects that.
Troubleshooting Occasionally you may have trouble with working your microscope. Here are some common problem and solutions. • 1.Image is too dark! • Adjust the diaphragm, make sure your light is on.
Troubleshooting • 2.there’s a spot in my viewing field, even when I move the slide the spot stays in the same place! • Your lens is dirty. Use lens paper, and only lens paper to carefully clean the objective and ocular lens. The ocular lens can be removed to clean the inside. The spot is probably a spec of dust.
Troubleshooting • 3.I cant see anything under high power! • Remember the steps, if you cant focus under the scanning and then low power, you wont be able to focus anything under high power . Start at scanning and walk through the steps again. • 4.Only half of my viewing field is lit, it looks like there’s a half-moon in there! • You probably don’t have your objective fully clicked into place.
