By stretching a thin strip of polished metal, as in a tension-testing machine, demonstrate and comment on what happens to its reflectivity as the strip is being stretched.

Obtain a number of small balls made of plastic, wood, marble, or metal, and arrange them with your hands or glue them together to represent the crystal structures shown in Figs. 1.3-1.5. Comment on your observations.

(a) (b) FIGURE 1.5 The hexagonal close-packed (hep) crystal structure: (a) unit cell and (b) single crystal with many unit cells.OO ich