The Microscope Agricultural Biology

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.

Microscope Unit Microscopic Terms

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).

Microscope Unit Use of the Microscope

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.

Microscope Unit Functions of Microscope Parts

Functions of Microscope Parts Ocular Lenses: Upper lenses nearest to eyes; magnify image already magnified by objective; brings light rays to a focus at the eye

Functions of Microscope Parts Rotating Nose Piece: Revolving part that supports three objectives with different magnifications

Functions of Microscope Parts Objective Lens: Lens closest to specimen; magnifies image of specimen

Functions of Microscope Parts Stage: Flat table-like area where slide or specimen is placed.

Functions of Microscope Parts Iris Diaphragm Lever: Disc-shaped device, located beneath stage, controls amount of light passing through specimen

Functions of Microscope Parts Condenser

Functions of Microscope Parts Substage Light: Source of light which passes through specimen.

Functions of Microscope Parts Base: Bottom stand, which houses the light.

Functions of Microscope Parts Body: Contains mirrors to reflect light to eyepiece.

Functions of Microscope Parts Head

Functions of Microscope Parts Arm: Basic frame, used to carry microscope.

Functions of Microscope Parts Thumb Clip: Hold slide on stage, to prevent it from slipping around.

Functions of Microscope Parts Mechanical Stage

Functions of Microscope Parts Coarse Adjustment Knob: Roughly focuses image by bringing the specimen and objective lenses closer together or farther apart.

Functions of Microscope Parts Fine Adjustment Knob: Sharpens image of specimen by moving specimen and objective lenses very small distances closer together or farther apart.

Functions of Microscope Parts Mechanical Stage Control

Functions of Microscope Parts Light Control