The Compound Microscope Flashcards
What are the two general categories of microscopes?
- Light Microscope
- Electron Microscope
Which general category of a microscope uses light waves and lenses?
Light Microscope
Which general category of a microscope employs electron beams and magnetic fields to produce an image?
Electron Microscope
How can light microscopes be classified as SIMPLE?
Light microscopes have a short focal length, are held close to the eye, and can magnify objects only up to 300x.
How can compound microscopes be classified?
Electron microscopes employ two separate lenses, an ocular and an objective, in order to achieve 2-5 times greater magnification.
Other types of microscopes include the ff: (5)
- Bright Field
- Dark Field
- Ultraviolet (UV)
- Fluorescent
- Phase-Contrast
___ is where the microscope field is brightly lighted and the object to be observed appears dark due to its ability to absorb or refract some of the incident light.
Bright Field
____ is where the object appears luminous against a dark background since it reflects some of the incident light in all directions.
Dark Field
The ___ is used principally to detect or even measure substances in specimens of living tissues that are known to absorb UV light at particular wavelengths. UV is not visible to the eye, so the image formed is recorded with the use of cameras or a television screen.
Ultraviolet (UV) Microscope
The ____ makes use of the property of certain chemical substances that release light at a different wavelength when exposed to UV rays. Such substances convert UV light into visible waves of greater length. Bacteria and other microorganisms are stained with fluorescent stain that can be detected in a microscope illuminated with UV light.
Fluorescent
The ____ utilizes the refraction that occurs when light passes from one medium into another of different density. The special objectives and condenser intensify slight differences in contrast produced by this bending of light. It is useful in studying the internal structures of microorganisms because structures differing in refractive index from the surrounding protoplasm become visible, and their sizes and locations can be determined.
Phase-Contrast
This part of the microscope keeps the microscope steady at any position of the stage.
Base
This part of the microscope is fastened to the base through the inclination joint; it permits the adjustment of the stage to a desired angle.
Arm
This part of the microscope reflects the light into the condenser.
Concave Mirror
This part of the microscope concentrates the light rays received from the mirror and sends them to the objective.
Condenser
This part of the microscope is a horizontal platform upon which the specimen to be examined is placed; at the center of the stage is a circular aperture.
Stage
These parts of the microscope hold the slide in place on the stage.
Stage Clips
This part of the microscope is part of the optical system of the microscope which produces the specimen’s initial magnified image (real) within the body tube.
Objective
What are the three objectives of a student microscope?
- Dry Low Power Objective
- Dry High Power Objective
- Oil Immersion Objective
The objectives of the student microscope are ____, they are corrected for the spectral colors of ___ and ___.
achromatic;
red and blue
What are the four (4) important features of the objectives?
- Focal Length
- Resolving Power
- Numerical Aperture (NA)
- Parfocal
The ____, an optical constant of the lens system, is the distance from the center of the lens to the point where parallel rays entering the lens are brought to a focus.
Focal Length
The ____ is that property to recognize features of a specimen that are close to each other as separate or distinct. The greater the resolving power, the greater the definition of an objective. This property is dependent on the wavelength of light used and an optical property of the objective lens known as a numerical aperture.
Resolving Power
The ____ is a measure of the resolving power of an objective. An objective with a 0.25 N.A. allows the viewer to distinguish as separate 25,000 lines per inch. If the specimen is known to be of the order of 26,000 lines per inch, the observer can never see the line as separate no matter how much magnification is employed. Lenses with higher magnification usually have higher N.A. but the medium through which the light passes also affects N.A. N.A. is indicated in the side of the lens.
Numerical Aperture (NA)
A ____ means that the objectives are optically ad mechanically designed so that the distance between the specimen and the aerial image is always constant. Slight refocusing with the aide of the fine focus knob is sufficient to restore critical sharpness of the image after changing from one objective to another, thus, the coarse focus knob need not to be operated.
Parfocal
The ____ to which the parfocal objectives are attached, allows convenient shifting of the objectives.
Revolving Nosepiece
The ____ is a hollow cylindrical tube through which light passes from the objective to the eyepiece. The upper portion of the body tube is called the draw tube.
Body Tube
The ___ is that part of the optical system through which the specimen is viewed.
Eyepiece or Ocular
The intermediate image projected by the objective is enlarged by the ____.
Eyepiece
Why is it referred to as a compound microscope?
The term compound microscope is derived from the fact that the specimen is magnified TWICE, first by the objective lenses and second by the eyepiece.
The final image formed by a compound microscope is a ____.
Virtual Image
If the magnifying power of the objective is 100x and the eyepiece is 10x, the total magnification will be ___.
1000x
The ____ is used to bring the objective into approximate focus.
Coarse Focus Knob
For maximum definition, the ___ is used.
Fine Focus Knob
The free space between the specimen surface and the objective is the ____.
Working Distance (mm)
True or False
The higher the magnification of the objective, the bigger the working distance.
False
The higher the magnification of the objective, the smaller the working distance.
True or False
The higher the power of the objective, the greater the area of the specimen surface included in the field of vision.
False
The higher the power of the objective, the lesser the area of the specimen surface included in the field of vision.
If a sharp image is not obtained despite the application of the procedure, it is possible that: (5)
- The fine focus knob has reached a stop.
- Focusing attempts are too rapid.
- The objective is covered with dried oil from the previous user.
- The cover slip is too thick.
- The slide is inverted.
What is the optimum thickness of a cover slip?
0.17 mm
Microscopic objects can be measured by means of an ___ or ____. Both must be calibrated first with the ____.
Ocular or Filar Micrometer; Stage Micrometer
The unit of linear measurement in microbiology is the ____, which is equivalent to ____ or _____.
Micrometer (µm); 1/1000mm or 1/25,400in
The ____ is a glass disc with a mounted scale. It may or may not have numbers on it. It is inserted into the eyepiece and must be calibrated for the particular objective, eyepiece, and tube length before
Ocular Micrometer (OM)
True or False
A student microscope has a fixed tube length.
True
A ____ is a glass slide with graduations of known intervals.
Stage Micrometer
Some micrometers have numbers to indicate the length of the divisions. One small division is ____, whereas one big division is _____.
0.01 mm or 10 µm; s 0.1 mm or 100 µm
