Presentation on theme: "The Microscope Agricultural Biology. The Microscope Two major types of microscopes based on energy used by device: 1.Light microscope Uses visible light."— Presentation transcript:
The Microscope Two major types of microscopes based on energy used by device: 1.Light microscope Uses visible light that is magnified as it passes through glass lenses Source: Light Magnifies up to 2000 times by using glass lenses Materials can be living or dead
The Microscope Two major types of microscopes based on energy used by device: 2.Electron microscope Electron beam passes through magnetic lenses before magnified image is projected on photographic film or a fluorescent screen similar to television. Source: Electrons Magnifies up to 2 million times by using magnets Materials should be dead
The Microscope You will use the compound microscope –W–Why is it “compound”? Two lenses collect and focus the light from the source as it is transmitted through the sample. For light to pass through the specimen, the specimen must be very thin. The image of the specimen seen in the microscope is not only magnified but the resolution is improved.
The Microscope Resolution: Ability to distinguish and separate fine details in a specimen, such as two objects that are close to each other as being two rather than one –O–Our eyes can “resolve” two objects that are at least 0.1 millimeters (mm) apart –A–A good light microscope has a resolution up to 1000 times closer or 0.1 micrometers (µm)
The Microscope Contrast: Ability to distinguish detail; different absorption of light by parts of the object being viewed –C–Can be increased by decreasing light intensity or by staining of the specimen Proper selection of stains also increases our ability to identify specific structures within specimen
Microscopic Terms Slide: Piece of glass upon which specimen is placed for viewing. Cover Slip: Thin square piece of glass or plastic used to cover specimen. Field of View: Area of specimen which is seen through lens system; bright circle you see when looking into a microscope.
Microscopic Terms Depth of Field: Ability of lens to furnish distinct image above and below focal plane. Decreases with increase of magnification. Parfocal: When objective is in focus, it can be switched from one power to another, with only small fine focus adjustments necessary
Microscopic Terms Magnification: Number of times an object’s apparent size is increased by lens system –D–Determined by multiplying power of objective by the power of eyepiece (usually 10x). Power of objective xPower of eyepiece (usually 10x) Total magnification
Microscopic Terms High Power: High power objective on nosepiece (usually 40x). Medium Power: Middle power objective on nosepiece (usually 10x). Low Power: Lowest power objective on nosepiece (usually 4x).
Use of the Microscope 1. Carry with both hands. 2. Set microscope in from edge of desk. 3. Use lens paper to clean eyepiece and objectives. 4. Start with lowest power (shortest objective) in place.
Use of the Microscope 5. Turn coarse adjustment so that stage is as close to low power as possible -- now while looking, turn coarse adjustment so stage starts to move away from objective. 6. Clean up all spills and moisture from stage before putting away.
Use of the Microscope 7. Caution – Keep all water away from electrical parts 8. Never use coarse adjustment with high power objective while trying to focus, because of danger of striking and breaking glass slide with objective.