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RHS Forensics Ch 4
Rockwall High School
| Question | Answer |
|---|---|
| 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
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