Chapter 15- Glass Examinations

Front 1

When glass is hit

Back 1

it can stretch slightly

Front 2

Refractive index comparisons result in circumstantial class evidence and

Back 2

cannot confirm guilt

Front 3

There is sophisticated technology that enables nondestructive analysis of glass. Which of these technologies can help determine the cause of an automotive collision by determining whether the headlights were on at the time of the collision?

Back 3

Scanning Electron Microscopy (SEM)

Front 4

As a bullet passes through glass, it pushes some glass ahead of it, causing a cone-shaped piece of glass to exit along with the bullet. The cone of glass makes the exit hole

Back 4

large than the entrance hole of the bullet

Front 5

The submersion method involves placing the glass fragments into different liquids of known refractive indexes. If a piece of glass and a liquid have the same refractive index, the glass fragment will seem

Back 5

to disappear when placed in the liquid

Front 6

If the refractive indexes of several different liquids are known, the

Back 6

submersion method can be used to estimate the refractive index of the glass

Front 7

True or False? Glass is a hard, amorphous material made by melting silicon dioxide, calcium oxide, and sodium oxide at very high temperatures

Back 7

True

Front 8

The refractive index is a measure of how light bends when it passes through

Back 8

one substance and into another

Front 9

Glass will break first on the weaker side, the side

Back 9

opposite the strike. Radial fractures will result

Front 10

When certain types of sand are exposed to extremely high temperatures, such as lightning strikes or volcanic eruptions, which type of glass can be formed?

Back 10

Obsidian glass

Front 11

A high-velocity bullet fired from a great distance will often exhibit characteristics of a ____________________ fired from a closer range.

Back 11

low-velocity bullet

Front 12

The angle at which a bullet enters a piece of window glass can help locate the position of the shooter. If the bullet was fired perpendicular to the windowpane, the entry hole of the bullet will be

Back 12

round

Front 13

True or False? Each type of glass has a density that is specific to the glass. One method of matching glass fragments is by a density comparison.

Back 13

False

Front 14

Light travels

Back 14

nearly as fast through air as it does through a vacuum

Front 15

True or False? The primary ingredient of glass is carbon dioxide

Back 15

False

Front 16

Silicon dioxide is

Back 16

the chemical name for silica

Front 17

_____________ is a combination of two or more types of glass, one hard and one soft. The softer layer makes the glass more elastic so It can flex instead of shatter.

Back 17

Bulletproof glass

Front 18

If the refractive index of the liquid medium is different than the refractive index of the piece of glass, a halo-like ring appears around the edge of the glass. The halo-effect is called a

Back 18

Becke Line

Front 19

One method of determining if the evidence glass matches the glass from the crime scene is to compare the

Back 19

refractive index of the evidence glass to the refractive index of the glass from the crime scene

Front 20

If several shots are fired through glass, the ________________________ in which the shots were fired can be determined if enough of the glass is available or can be reconstructed.

Back 20

order

Front 21

Density of glass is calculated by dividing the

Back 21

mass of a substance by its volume

Front 22

The speed of an object when it hits a piece glass influences the number and locations of concentric circles in the fracture pattern. An object moving at high speed upon impact, such as the bullet, produces

Back 22

tighter concentric circles

Front 23

_____________________________ is also known as tempered glass. It is used in car windows, shower doors, and glass tables. As it has been subjected to extreme temperature or chemical treatments, it has improved strength

Back 23

Safety Glass

Front 24

True or False? Glass is called an amorphous solid because its atoms are arranged in a random fashion.

Back 24

True

Front 25

True or False? Fine glassware and decorative art glass, called crystal or leaded glass, contain lead oxide rather than calcium oxide.

Back 25

True