Glass

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  • Created by: Ashlee
  • Created on: 03-05-15 21:18
What are the properties of glass?
Variety of chemical compositions; transparent and translucent materials composed of fused inorganic materials
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How does glass break?
Struck; bends; fracture (radial); stress (concentric fractures); continues until stops
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How do you collect glass at a crime scene?
Take from window not floor; toughened = 50 pebbles; soda lime = 6 pieces
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What is refractive index?
Ration between speed of light in vacuum and speed of light through medium
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What is the equation to work out RI?
n = C/v
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How is RI measured?
Immersion method to see if the RI is the same as the oil around it
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What is the RI of glass?
1.510
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What is the probative value of glass?
Physical, optical and elemental characteristics
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What is soda lime glass composed of?
Silica, soda and lime
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What items are made of soda lime?
Windows, drinks, containers
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Why is toughened glass "tough"?
High boron content; increased bending strength; resistant to thermal shock; super heated and rapidly cooled
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When is toughened glass used?
On car windows/windscreens
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Why is glass of evidential value?
Sequence of events; type of weapon used; direction of force; distribution of glass; associated evidence (victim, scene and suspect)
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How would you analyse glass?
Microscope; UV light
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What would you specifically look for when analysing glass?
Colour; thickness; curvature; fractures; uniformity; surface conditions; radial fractures; rear surface; right angles; backward fragmentation
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What are the 3 rules when analysing glass?
Radial fracture, right angles, rear surface
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Why would you use UV light to analyse glass?
Tin diffuses into glass due to float glass manufacture process and fluoresces under UV light
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Other cards in this set

Card 2

Front

How does glass break?

Back

Struck; bends; fracture (radial); stress (concentric fractures); continues until stops

Card 3

Front

How do you collect glass at a crime scene?

Back

Preview of the front of card 3

Card 4

Front

What is refractive index?

Back

Preview of the front of card 4

Card 5

Front

What is the equation to work out RI?

Back

Preview of the front of card 5
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