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RHS Forensics Ch 4

Rockwall High School

How much glass should be collected from scene? If you think pieces can be put back together then collect as much as possible, if not then only collect 1 sq. inch
What 2 properties characterize light? frequency and wavelength
How can you determine which crack was first? The radial fractures terminate at the cracks of the former
What is regular glass made of? Sand (Sodium oxide), and various metal oxides
3R Rule Radial cracks form Right angles on the Reverse side
Borosilicates (Pyrex glass) heat-resistant glass used for automobile heeadlights
Float glass Molten glass cooled on molten tin (flat glass used for windows)
Soda-Lime glass most window and bottle glass
If weight increases does mass also increase? YES
Which changes... Mass or weight? WEIGHT
# of known compounds 16 million
# of elements 118
# of naturally occurring elements 89
1 kilogram= _____ pounds 2.2 pounds
1 liter=_______ quarts 1.06 quarts
1 pound=______ grams 453.6 grams
1 meter=_______ inches 39.57 inches
1 inch=______ centimeters 2.54 cm
grams unit for mass (metric)
meters unit for length (metric)
liters unit for volume (metric)
Amorphous solid constituent atoms or MOLECULES arranged in random positions
Physical property how a substance behaves on its own
chemical property how a substance behaves with other substances
matter anything that has mass and takes up space
element fundamental principle of matter that cannot be broken down into simpler chemical means
atom smallest unit of an element
compound pure substance composed of two or more substances
all living things are made up of... carbon
physical state solid, liquid, or gas
solid molecules held closely together by strong attractive forces
liquid forces are strong enough to keep molecules in tact, but too weak to hold them rigidly in place
gas (vapor) attractive forces between molecules are weak enough to permit them to move freely
sublimation direct state change from solid to gas (example: dry ice)
phase uniform substance separated by definite visible boundaries
wavelength distance between crests
frequency also known as speed, is the # of waves that pass a given point in a given time
dispersion separation of light into component wavelengths ( slowed down to a different speed)
refraction bending of light wave caused by change in speed (after dispersion when the light changes speed and slows down, causing components to bend at different angles)
visible light colored light (ROYGBIV), backwards on electromagnetic spectrum (VIBGYOR)
electromagnetic spectrum entire range of radiation
Gamma Rays short wavelength, high energy, high frequency
X-rays after gamma rays
ultraviolet after x-rays
visible light (order in spectrum) after ultraviolet
infrared after visible light
microwaves after infrared
radio waves long wavelength, low energy, low frequency
LASER acronym for Light Amplification by Stimulated Emission of Radiation ( light that has all waves pulsing in unison)
photon particle of light (discrete particle of electromagnetic radiation)
Farenheit Scale melting pt= 32 degrees boiling pt= 212 degrees 180 degree divisions
Celcius Scale melting pt=0 degrees boiling pt= 100 degrees 100 degree divisions
weight force with which gravity attracts a body
mass amount of matter in an object
density intensive physical property (D=M/V)
intensive property property that does NOT depend on the size of an object
refractive index ratio of speed of light in a vacuum to its given speed in a given medium, (INTENSIVE PROPERTY)
crystalline solid constituent atoms are regularly arranged
Birefringence difference in 2 indexes of refraction exhibited by most crystalline solids
tempered glass glass to which strength is added through stress by rapid heating and cooling
laminated glass 2 pieces of regular glass with plastic between them (windshields)
Becke Line bright halo observed near border of a particle immersed in a liquid of a different refractive index
Radial fracture crack in glass that extends outward like the spoke of a wheel
concentric crack crack in glass that forms a rough circle around the point of impact
Flotation method reference glass in BROMOFORM/BROMOBENZENE mix, mix adjusted till glass suspended, then suspect glass of similar size and shape is added, if suspect sinks, then the density is greater than both the sample and the mix
disappearance of Becke Line after the mix and sample are of the same density in the flotation method and suspended this is called the MATCH POINT. The halo disapears when the mix and sample have similar refractive indexes
How do you change the refractive index of the immersion fluid? by adjusting the temperature by heating it on a hot stage
GRIM 3 (Glass Refractive Index Measurements)FBI database that correlates value freq of occurance of glass population once comparison of frag is done u can correlate density& refractive index to freq of occurance & get probability that glass came from same source
Created by: ocorneau