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25 Cards in this Set
- Front
- Back
When glass is hit
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it can stretch slightly |
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Refractive index comparisons result in circumstantial class evidence and
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cannot confirm guilt |
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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? |
Scanning Electron Microscopy (SEM)
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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 |
large than the entrance hole of the bullet |
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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 |
to disappear when placed in the liquid |
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If the refractive indexes of several different liquids are known, the
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submersion method can be used to estimate the refractive index of the glass |
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True or False? Glass is a hard, amorphous material made by melting silicon dioxide, calcium oxide, and sodium oxide at very high temperatures |
True |
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The refractive index is a measure of how light bends when it passes through |
one substance and into another |
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Glass will break first on the weaker side, the side |
opposite the strike. Radial fractures will result |
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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? |
Obsidian glass |
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A high-velocity bullet fired from a great distance will often exhibit characteristics of a ____________________ fired from a closer range.
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low-velocity bullet
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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 |
round |
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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. |
False
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Light travels |
nearly as fast through air as it does through a vacuum
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True or False? The primary ingredient of glass is carbon dioxide
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False |
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Silicon dioxide is |
the chemical name for silica |
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_____________ 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.
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Bulletproof glass |
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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
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Becke Line
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One method of determining if the evidence glass matches the glass from the crime scene is to compare the |
refractive index of the evidence glass to the refractive index of the glass from the crime scene |
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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. |
order |
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Density of glass is calculated by dividing the |
mass of a substance by its volume |
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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
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tighter concentric circles |
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_____________________________ 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 |
Safety Glass
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True or False? Glass is called an amorphous solid because its atoms are arranged in a random fashion.
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True |
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True or False? Fine glassware and decorative art glass, called crystal or leaded glass, contain lead oxide rather than calcium oxide. |
True |