1. CJO3 EOC Review 2014-2015

2. Unit 11 – Glass O 25.07 – Describe broken glass examination procedures

3. What are general properties of glass? O Hard solid O Made by melting sand and lime at very high temperatures O Can be polished, ground, or cut once cooled O Amorphous material – Has an irregular atomic structure O Breaks in a variety of fracture patterns

4. What properties of glass allow for comparisons? O Chemical composition/properties O Shatter patterns O Thickness O Color O Density O Refractive index

5. What is the formula for calculating density? O D = m/V O D = Density (g/ml) O m = Mass (grams) O V = Volume (milliliters)

6. How is mass measured for purposes of calculating density? O By using a balance

7. How is volume measured for purposes of calculating density? O By placing the glass fragments into a beaker filled with water and measuring the overflow in a graduated cylinder

8. How is refractive index calculated? O Snell’s Law O Becke Lines

9. What is the formula for Snell’s Law? O n 1 (sine angle 1) = n 2 (sine angle 2) O n 1 = 1 (refractive index of air) O Angle 1 = Angle of incidence O n 2 = refractive index of glass O Angle 2 = Angle of refraction

10. What is a Becke Line and how is it interpreted? O A halo-like effect appearing on the edge of a glass fragment when submerged in a liquid of differing refractive index O Line inside the glass = Glass refractive index is higher than the liquid O Line outside the glass = Glass refractive index is lower than the liquid

11. What are radial fractures and how can they help determine direction of travel? O Impact fractures O Appear 1 st O Found on opposite side of force O Create straight lines that extend from the point of impact

12. What are concentric fractures and how can they help determine direction of travel? O Impact fractures O Appear 2 nd O Found on the same side as the force O Create circular lines around the point of impact

13. In reference to bullet holes, how else can direction of travel be determined? O Examine the cone-shaped hole O Larger side = Exit O Smaller side = Entry O Angle = Possible shooter position

14. How can bullet holes be sequenced? O Examine the fracture lines O A new fracture line will always stop when it reaches an existing one