i. Anisotropy:
a. The ability of crystalline solids to change values of physical properties when measured in different directions is called anisotropy.
b. For crystalline solids, the physical properties like refractive index, electrical conductance, dielectric constant, etc., are different in different directions. As the direction changes (MN, OP, QR, etc.), the composition of the medium changes. This results in anisotropy.
ii. Unit cell:
a. Crystalline solids are aggregates of many small, tiny crystals. These tiny crystals are called unit cells.
b. A unit cell is a basic repeating structural unit of a crystalline solid.
