BioLab3 Lab Report 3 Microscope and the Cell Student Name: _____________ ___________________________ I. Purpose of the Microscope Define the following terms. Magnification The degree to wh ich the image of a specimen is
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BioLab3 Lab Report 3 Microscope and the Cell Student Name: _____________ ___________________________ I. Purpose of the Microscope Define the following terms. Magnification The degree to wh ich the image of a specimen is enlarged. Resolution The ability to distinguish two objects as separate and distinct. Contrast The ability to see specimen detail against its background. Stains and dyes are added to sections of biological specimens to increase contrast. II. The Compound Microscope EXERCISE 1 – Label the parts of the compound microscope 1. Ocular Eye piece 2. arm 3. Coarse adjustment knob 4. Fine adjustment knob 5. Revolving nose piece 6. Objective lens 7. Stage clips 8. stage 9. Iris diaphragm lever 10. Condenser lens 11. In-base illuminator (light) 12. base Define the following terms. Eyepiece Located in the upper end of the body tube and focuses light on the retina of the eye. The power of the eye piece is usually 10x. Arm Functions as the handle of the microscope. Course adjustment knob Large knob used to make large movements of the objective lens when focusing on a specimen. Fine adjustment knob Located either on top of the coarse adjustment knob or separately. Manipulating this knob clarifies detail of the specimen. Revolving nosepiece Circular structure that houses the objective lenses. Threaded allows for ease of movement between lenses. Objective lenses Attached to the revolving nose piece. Power of the objective lens is usually 4x, 10x, 40x and 100x. Stage clips Attached to the stage and used to secure the slide in position. Stage Large platform below the revolving nosepiece. The microscope slide is placed on the stage. Iris diaphragm lever Shutter like device below the stage that regulates the amount of light passing through a specimen. Condenser Located under the diaphragm and the stage aperture. Converges light rays from the light source so that they pass through the specimen on the slide and into the objective lens. Light source Located in the base of the microscope. Base Lower most part of the microscope in contact with the table. EXERCISE 2 – Calculate microscope magnification Calculate the magnification for the combined eyepiece and objective lens in the table. Eyepiece Lens Magnification Objective III. Viewing Microscope Slides EXERCISE 3 – Focusing the microscope Define the following terms. Temporary wet mount Prepared in the laboratory. Permanent mount Prepared by a biological supply house. Parcentral Property of the microscope. Prepared slide, view from the side and position the specimen directly over the aperture of the stage. Specimen remain centralized in the field of view from one objective lens to the next lens. Parfocal The ability of the microscope to remain in focus when switching from one objective lens to the next highest power. EXERCISE 4 – Specimen orientation Step 4: With the scanning lens in place, the prepared slide is moved to the right while watching the image through the microscope. • In which direction does the image move? Moved to the left. Step 5: The slide is moved away from you. • In which direction does the image move? Goes toward you. • What is the relationship between the movement of the image and the object? Moves the opposite way. IV. Depth of Focus EXERCISE 5 – Determine depth of focus Step 5: Determine the order of the colored threads and enter your results below: Top Blue Middle Red Bottom yellow • How is the order of the crossed threads determined? This is normally done by using the fine adjustment knob and focusing from the bottom most thread toward the top of the slide. • What diaphragm adjustment should be made to more easily determine the order of the colored threads? Usage of more light. • Explain how depth of focus can be used to reconstruct structure. ----------crossed threads
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