Ch. 5 Forensic Analysis of Glass

Question 1

amorphous solid

Answer 1

a solid in which the atoms have a random, disordered arrangement

Question 2

annealing

Answer 2

heat treatment that produces tempered glass

Question 3

compressive force

Answer 3

force that squeezes glass

Question 4

concentric cracks

Answer 4

cracks that appear as an imperfect circle around the point of fracture

Question 5

crystalline solid

Answer 5

a solid in which the atoms are arranged in a regular order

Question 6

density gradient tube

Answer 6

a tube filled with liquids with successively higher density

Question 7

entrance side

Answer 7

the load side of a projectile

Question 8

exit side

Answer 8

the unloaded side of a projectile

Question 9

fracture match

Answer 9

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

Question 10

laminated glass

Answer 10

two sheets of glass bonded together with a plastic sheet between them

Question 11

Mohs scale

Answer 11

a scale that measures the hardness of minerals and other solids

Question 12

projectile

Answer 12

the load of a bullet shot at a pane of glass

Question 13

radial cracks

Answer 13

cracks that radiate in many directions away from the point of fracture

Question 14

refractive index

Answer 14

ratio of the speed of light in air to the speed of light in another material (such as glass)

Question 15

rib marks

Answer 15

the set of curved lines that are visible on the edges of broken glass

Question 16

shear force

Answer 16

force that moves one part of the material in one direction while another part is moving in a different direction

Question 17

striations

Answer 17

fine scratches left on bullets, formed from contact of the bullet with imperfections inside the gun barrel

Question 18

tangential cracks

Answer 18

cracks that appear as an imperfect circle around the point of fracture

Question 19

tempered glass

Answer 19

glass that has been heat treated to give it strength

Question 20

tensile force

Answer 20

force that expands the material

Question 21

Glass is often found on burglary suspects as _____ evidence.

Answer 21

transfer

Question 22

Glass is a solid that is not crystalline, but rather a(n) _____ solid.

Answer 22

amorphous

Question 23

The atoms of an amorphous solid have a(n) ______, ______ arrangement.

Answer 23

random, disordered

Question 24

Tampered glass is rapidly ______, which makes the surface and edges compress.

Answer 24

cooled

Question 25

Automobile windshield glass is laminated with a(n) ______ layer between two layers of glass.

Answer 25

vinyl plastic film

Question 26

When a sheet glass is rolled, the rollers leave parallel ______ marks in the surface.

Answer 26

striation or ream marks

Question 27

The thickness of a questioned glass sample can be measured with a(n) ______.

Answer 27

micrometer

Question 28

The accepted scale of glass hardness is the ______ scale.

Answer 28

Mohs

Question 29

On the Mohs scale, the softest material, ______, is given the value of 1, and the hardest material, diamond, is given a value of ______.

Answer 29

talc, 10

Question 30

A force that squeezes glass is called a(n) ______ force.

Answer 30

compressive

Question 31

A(n) ______ force expands glass.

Answer 31

tensile

Question 32

A force that slides one part of glass in one direction and another part in a different direction is called a(n) ______ force.

Answer 32

shear

Question 33

A(n) ______ crack radiates outward, away from the load point.

Answer 33

radial

Question 34

A(n) ______ grows from one radial crack to another and from the loaded side to the unloaded side.

Answer 34

concentric

Question 35

When comparing glass fragments for the purpose of matching their color, the fragments should be viewed on ______ over a white surface.

Answer 35

edge

Question 36

The refractive index is a measure of how much light is ______ as it enters a material.

Answer 36

bent or refracted

Question 37

The bending of a light beam as it passes from air into glass is known as ______.

Answer 37

refraction

Question 38

The ______ and ______ of the light being refracted influence the refractive index for any substance.

Answer 38

temperature, wavelength

Question 39

The D line, which is used to designate the refractive index, indicates ______.

Answer 39

sodium lamp 589nm wavelength

Question 40

The oil immersion method of refractive index measurement uses ______ oils.

Answer 40

silicone

Question 41

For the oil immersion method of refractive index measurement, the refractive index of the immersion oil is varied by raising its ______.

Answer 41

temperature

Question 42

The halo that is observed around the glass fragment in the oil immersion method is known as the ______ line.

Answer 42

Beche

Question 43

The Emmons procedure for measuring the refractive index of glass makes measurements at three different ______ of light.

Answer 43

wavelengths

Question 44

By using a(n) ______ microscope, the Emmons procedure increases the precision of the refractive index measurements.

Answer 44

phase-contrast

Question 45

Heating glass in a furnace at temperatures above 600 degrees Celsius is called ______.

Answer 45

annealing

Question 46

The scanning electron microscope cannot take precise measurements of elemental concentrations in glass fragments because of the ______ of the glass fragments.

Answer 46

irregular shape