Glass Quiz 10/27/2014

1. What are the two most useful physical properties of glass for forensic comparisons? Density and Refractive index.

2. _________________ glass fragments into small squares, “dices”, with little splintering when broken. Tempered

3. Glass fracture lines that encircle the hole in the glass are known as _____________________ fractures? concentric

4. When glass’s elastic limit is exceeded, the first fractures develop into radial lines on the surface of the (same,opposite) side to that of the penetrating force. opposite

In order to determine the refractive index of a small piece of glass, the glass is submerged in different liquids and viewed under a microscope. The appearance of a Becke line is used to determine the refractive index (RI). What is the Becke line? What does the location of the Becke line tell you about the RI of the fragment and the surrounding liquid? Halo of light surrounding the glass when the RIs are not the same. Gives a relative RI to the liquid and the glass based on the position of the halo.

6. A beam of light passes through air into a second medium at an angle of 48°. The angle of refraction is measured at 33°. What is RI of the medium? If angle of incidence was 33 and angle of refraction 48 RI=0.733 If angle of incidence was 48 and angle of refraction 33 RI=1.36

Jared the investigator arrives at the scene of a hit and run collision Jared the investigator arrives at the scene of a hit and run collision. The driver who remained at the scene reports that the windshield or a side window of the car that struck him shattered on impact. Jared searches the accident site and collects a large number of fragments of tempered class. This is the only type of glass recovered from the scene. How can the glass evidence help Jared locate the vehicle? Which window was likely broken? Look for broken glass.s

Which order were the bullet holes made? Justify your answer. D, B, A, C