Flashcards in Forensic Microscopy Deck (47):
The term “microscopy” describes:
Analytical approach in, which a microscope plays a central role in maximizing the extraction of useful information from a variety of samples.
The integration microscopical techniques with other instrumentation results in:
Powerful and versatile combination that cannot otherwise be equaled.
The microscope is routinely employed in areas of criminalistics for:
Document examination, tool mark comparison, firearms identification, serology, drug chemistry and trace evidence.
Good criminalistic technique demands the effective use of the:
Among the types of problems faced by the forensic microscopist or criminalist dealing with trace evidence are the:
- Characterization, identification and comparison of such and evidence types as paint, soil, minerals, dusts, glass, polymers, fibers (synthetic and natural), paper, starches, wood, hairs, pollens and trichomes.
A converging (or positive) lens can form images in two ways. These are termed:
Real and virtual images.
A ___________image is formed on the side of the lens opposite the object and is inverted with respect to the object.
An image is_____________in the sense that knight rays from the object actually converge at a given plane in space and thus the image can be made to fall on a screen.
The image produced by a movie or slide projector is a ___________image.
When a lens is used as a magnifying glass, a _____________image is formed.
The ____________is erect and cannot be directly registered on a screen or a piece of film.
The use of another lens is necessary to convert a ____________image into a real image so it can be projected onto files or some other sensitive surface.
The simple microscope, in which magnification takes place in one stage, is no more than a _________________.
The most common simple microscopes in use today are low powered types such as:
Hand lenses, eye loupes, linen testers and fingerprint magnifiers.
Compound microscopes have extremely short_____________lengths.
Compound microscopes can produce large___________________.
The principle of the compound microscope was developed and used successfully by:
Producing lenses of shorter focal length with high power requires that:
Radius of curvature and size of lens be decreased
With a small short focal length lens placed closed to the eye, refractive index inhomogeneities within the eye are accentuated.
Modern compound microscopes circumvent accentuation by having magnification take place in ___________stages.
The performance of the compound microscope did not surpass that of a simple microscope as a research tool until the introduction of the____________.
The last stage of magnification in the compound microscope is the same as for the____________microscope. A __________is formed and it takes place in the eyepiece (ocular).
An increase in magnification that continues to reveal details in the object is called:
Additional magnification that merely results in a larger image with no further detail is known as:
The two most common microscopes in the laboratories are:
Biological and stereoscopic binocular
The stereoscopic binocular or stereo microscope is the most widely used instrument in the crime laboratory.
The ____________is often the first instrument employed to make a preliminary evaluation of evidence or to sort and select items for further scrutiny.
Stereo Binocular microscope
The most common type of illumination employed with the stereo microscope is variously termed:
Incident, reflected, vertical or epi
The biological microscope is designed for_______________light illumination. It is not suitable for most thick or opaque specimens.
The ________________microscope is the most versatile and powerful tool available for analyzing trace evidence.
Comparison microscopes find extensive use in forensic laboratories.
A comparison microscope is basically two carefully matched ____________________.
Images produced by two compound microscopes are____________in a common intermediate field plane within the ocular (s). In this way, objects from two different fields of view can be compared directly.
______________distinct types of comparison microscopes find use in forensic laboratories. One is designed for comparison of __________objects such as bullets, cartridge cases and tool marks at low to moderate magnification; this type uses_________________.
The second type of comparison microscope is used for:
Hair and fiber comparisons (transmitted light illumination)
Magnification (comparison microscopes)on each side can be compared by using known scales such as _______________.
_________________illumination is when the specimen is illuminated from the side opposite of the objective.
Everyday objects are normally viewed in the macro world using ________________.
A compound microscope should have the following transmitted light illumination attributes:
- Capable of illuminating the specimen uniformly with adequate intensity, allow precise control of light paths so the only area of the specimen being examined is illuminated; and angularity is appropriate for the objective used.
Precise control of illumination permits____________for varied conditions and results in a reduction of ______________resulting in diminished glare.
Two primary components supply illumination in most microscopes:
Illuminator and substage condenser
The most desirable illumination for a wide variety of applications was devised by:
August Kohler (1866-1948)
6 volts is the nominal operating voltage for a high quality microscope illuminator.
There is a considerable degree of interdependence among:
Resolution, magnification and visibility.
It is often not possible to effect an improvement in one without giving up optimum performance to the other.
Interference microscopes involve:
Two beams of light are separated and brought back together to form the image.
One beam contains the sample; the other is a reference beam.
The Phase Contrast Microscope can be thought of as the first ___________________.
Interference Contrast Microscope