Ch. 5 Forensic Analysis of Glass Flashcards
amorphous solid
a solid in which the atoms have a random, disordered arrangement
annealing
heat treatment that produces tempered glass
compressive force
force that squeezes glass
concentric cracks
cracks that appear as an imperfect circle around the point of fracture
crystalline solid
a solid in which the atoms are arranged in a regular order
density gradient tube
a tube filled with liquids with successively higher density
entrance side
the load side of a projectile
exit side
the unloaded side of a projectile
fracture match
the alignment of the edges of two or more pieces of glass, indicating that at one time the pieces were part of one sheet of glass
laminated glass
two sheets of glass bonded together with a plastic sheet between them
Mohs scale
a scale that measures the hardness of minerals and other solids
projectile
the load of a bullet shot at a pane of glass
radial cracks
cracks that radiate in many directions away from the point of fracture
refractive index
ratio of the speed of light in air to the speed of light in another material (such as glass)
rib marks
the set of curved lines that are visible on the edges of broken glass
shear force
force that moves one part of the material in one direction while another part is moving in a different direction
striations
fine scratches left on bullets, formed from contact of the bullet with imperfections inside the gun barrel
tangential cracks
cracks that appear as an imperfect circle around the point of fracture
tempered glass
glass that has been heat treated to give it strength
tensile force
force that expands the material
Glass is often found on burglary suspects as _____ evidence.
transfer
Glass is a solid that is not crystalline, but rather a(n) _____ solid.
amorphous
The atoms of an amorphous solid have a(n) ______, ______ arrangement.
random, disordered
Tampered glass is rapidly ______, which makes the surface and edges compress.
cooled
Automobile windshield glass is laminated with a(n) ______ layer between two layers of glass.
vinyl plastic film
When a sheet glass is rolled, the rollers leave parallel ______ marks in the surface.
striation or ream marks
The thickness of a questioned glass sample can be measured with a(n) ______.
micrometer
The accepted scale of glass hardness is the ______ scale.
Mohs
On the Mohs scale, the softest material, ______, is given the value of 1, and the hardest material, diamond, is given a value of ______.
talc, 10
A force that squeezes glass is called a(n) ______ force.
compressive
A(n) ______ force expands glass.
tensile
A force that slides one part of glass in one direction and another part in a different direction is called a(n) ______ force.
shear
A(n) ______ crack radiates outward, away from the load point.
radial
A(n) ______ grows from one radial crack to another and from the loaded side to the unloaded side.
concentric
When comparing glass fragments for the purpose of matching their color, the fragments should be viewed on ______ over a white surface.
edge
The refractive index is a measure of how much light is ______ as it enters a material.
bent or refracted
The bending of a light beam as it passes from air into glass is known as ______.
refraction
The ______ and ______ of the light being refracted influence the refractive index for any substance.
temperature, wavelength
The D line, which is used to designate the refractive index, indicates ______.
sodium lamp 589nm wavelength
The oil immersion method of refractive index measurement uses ______ oils.
silicone
For the oil immersion method of refractive index measurement, the refractive index of the immersion oil is varied by raising its ______.
temperature
The halo that is observed around the glass fragment in the oil immersion method is known as the ______ line.
Beche
The Emmons procedure for measuring the refractive index of glass makes measurements at three different ______ of light.
wavelengths
By using a(n) ______ microscope, the Emmons procedure increases the precision of the refractive index measurements.
phase-contrast
Heating glass in a furnace at temperatures above 600 degrees Celsius is called ______.
annealing
The scanning electron microscope cannot take precise measurements of elemental concentrations in glass fragments because of the ______ of the glass fragments.
irregular shape
