the microscope agricultural biology. the microscope two major types of microscopes based on energy...

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– 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– Our eyes can “resolve” two objects that are at

least 0.1 millimeters (mm) apart

– 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–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– Determined by multiplying power of objective by

the power of eyepiece (usually 10x).

Power of objective

x Power 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 Microscope1. 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.


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.


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


• 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


• Condenser


• Substage Light: Source of light which passes through specimen.


• Base: Bottom stand, which houses the light.


• Body: Contains mirrors to reflect light to eyepiece.


• Head


• Arm: Basic frame, used to carry microscope.


• Thumb Clip: Hold slide on stage, to prevent it from slipping around.


• 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.


• Mechanical Stage Control


• Light Control

the microscope agricultural biology. the microscope two major types of microscopes based on energy...

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