Question

Sodium dihydrogen phosphate is a hexagonal crystal. Mention how many optic axis and refractive indices are possible for the crystal

Answer 1

On the basis of the lengths and directions of the axes of the symmetry, all the crystals may be classified into the following 7 systems:

1 cubic crystal

2 Tetragonal crystal

3 orthorhombic crystal

4 Monoclinic crystal

5 Triclinic crystal

6 Rhombohedral crystal

7 hexagonal crystal :in this crystal the 3 axes of unit cell are equal in one plane at 120° with each other as fourth axis is perpendicular to this plane , that is a=b not equal to c and

Alpha =beta=90°, gamma=120.

The hexogonal system has 4 crystallographic axes consisting of 3 equal horizontal, or equilateral axes at 120° to each other, as well as one vertical axis which is perpendicular to the 3.this vertical axis can be longer or shorter than the horizontal axes.