Forensic Microscopy Flashcards Preview

Instrumentation of Trace Evidence > Forensic Microscopy > Flashcards

Flashcards in Forensic Microscopy Deck (47):
1

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.

2

The integration microscopical techniques with other instrumentation results in:

Powerful and versatile combination that cannot otherwise be equaled.

3

The microscope is routinely employed in areas of criminalistics for:

Document examination, tool mark comparison, firearms identification, serology, drug chemistry and trace evidence.

4

Good criminalistic technique demands the effective use of the:

Microscope

5

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.

6

A converging (or positive) lens can form images in two ways. These are termed:

Real and virtual images.

7

A ___________image is formed on the side of the lens opposite the object and is inverted with respect to the object.

Real

8

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.

Real

9

The image produced by a movie or slide projector is a ___________image.

Real

10

When a lens is used as a magnifying glass, a _____________image is formed.

Virtual

11

The ____________is erect and cannot be directly registered on a screen or a piece of film.

Virtual

12

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.

Virtual

13

The simple microscope, in which magnification takes place in one stage, is no more than a _________________.

Magnifying glass

14

The most common simple microscopes in use today are low powered types such as:

Hand lenses, eye loupes, linen testers and fingerprint magnifiers.

15

Compound microscopes have extremely short_____________lengths.

Focal

16

Compound microscopes can produce large___________________.

Magnifications

17

The principle of the compound microscope was developed and used successfully by:

Leeuwenhoek (1632-1723)

18

(Compound Microscope)
Producing lenses of shorter focal length with high power requires that:

Radius of curvature and size of lens be decreased

19

(Compound microscope)
With a small short focal length lens placed closed to the eye, refractive index inhomogeneities within the eye are accentuated.

True

20

Modern compound microscopes circumvent accentuation by having magnification take place in ___________stages.

Two

21

The performance of the compound microscope did not surpass that of a simple microscope as a research tool until the introduction of the____________.

Achromatic Lenses

22

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).

Simple
Virtual

23

An increase in magnification that continues to reveal details in the object is called:

Useful magnification

24

Additional magnification that merely results in a larger image with no further detail is known as:

Empty magnification

25

The two most common microscopes in the laboratories are:

Biological and stereoscopic binocular

26

The stereoscopic binocular or stereo microscope is the most widely used instrument in the crime laboratory.

True

27

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

28

The most common type of illumination employed with the stereo microscope is variously termed:

Incident, reflected, vertical or epi

29

The biological microscope is designed for_______________light illumination. It is not suitable for most thick or opaque specimens.

Transmitted

30

The ________________microscope is the most versatile and powerful tool available for analyzing trace evidence.

Polarized Light

31

Comparison microscopes find extensive use in forensic laboratories.

True

32

A comparison microscope is basically two carefully matched ____________________.

Compound microscopes

33

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.

Juxtaposed

34

______________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_________________.

Two
Opaque
Incident

35

The second type of comparison microscope is used for:

Hair and fiber comparisons (transmitted light illumination)

36

Magnification (comparison microscopes)on each side can be compared by using known scales such as _______________.

Stage micrometers

37

_________________illumination is when the specimen is illuminated from the side opposite of the objective.

Transmitted Light

38

Everyday objects are normally viewed in the macro world using ________________.

Reflected Light

39

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.

40

Precise control of illumination permits____________for varied conditions and results in a reduction of ______________resulting in diminished glare.

Optimization
Stray Light

41

Two primary components supply illumination in most microscopes:

Illuminator and substage condenser

42

The most desirable illumination for a wide variety of applications was devised by:

August Kohler (1866-1948)

43

6 volts is the nominal operating voltage for a high quality microscope illuminator.

True

44

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.

45

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.

46

The Phase Contrast Microscope can be thought of as the first ___________________.

Interference Contrast Microscope

47

_______________won the Nobel Peace Prize for Physics in 1953 for his invention and development of the phase contrast microscope which he perfected between 1935 and 1942.

Dutch Physicist Frits Zernike (1888-1966)