Across
- 3. a layer of plastic over a flat surface
- 5. glass made by volcanos
- 7. the throwing back by a body or surface of light
- 9. Impenetrable by bullets
- 10. how much the speed of light changes through material
- 12. glass is in a lot of vehicles
- 13. heating lead and calcium oxide
Down
- 1. the distance between opposite sides of something
- 2. a hard, brittle substance, typically transparent or translucent
- 4. without a clearly defined shape or form
- 6. circles arcs or other shapes which share the same center
- 7. arranged like rays or the radii of a circle
- 8. mass per unit area
- 11. glass made by lightning