91Ó°ÊÓ

If the atoms or molecules in a solid are periodical at regular intervals of distances in three dimensions, then that solid is known as (a) crystalline solid (b) amorphous solid (c) liquid crystals (d) none

Unit cells for most of the crystals are (a) spherical (b) elliptical (c) parallelopiped (d) none

Crystallographic axes are obtained by the intersection of non-coplanar faces of the unit cell. (a) three (b) four (c) five (d) six

The number of crystal systems is (a) 5 (b) 7 (c) 14 (d) 21

The number of Bravais lattices is (a) 256 (b) 7 (c) 14 (d) 37

Orthorhombic crystal system is represented by (a) \(a=b=c\) (b) \(a \neq \underline{b} \neq c\) (c) \(a \neq b \neq c\) (d) \(a \neq b \neq c\) \(\alpha=\beta=\gamma=90^{\circ}\) \(\alpha=\beta=\gamma=90^{\circ}\) \(\alpha=\beta=\gamma \neq 90^{\circ} \quad \alpha \neq \beta \neq \gamma \neq 90^{\circ}\)

Tetragonal crystal system is represented by (a) \(a=b \neq c\) (b) \(a \neq b \neq c\) (c) \(a \neq b=c\) (d) \(a=b=c\) \(\alpha=\beta=\gamma=90^{\circ} \quad \alpha=\beta=\gamma=90^{\circ} \quad \alpha=\beta=\gamma \neq 90^{\circ} \quad \alpha=\beta=\gamma=90^{\circ}\)

Triclinic crystal system is represented by (a) \(a \neq b \neq c\) (b) \(a \neq b=c\) (c) \(a=b \neq c\) (d) \(a \neq b \neq c\) \(\alpha \neq \beta \neq \gamma \neq 90^{\circ} \quad \alpha \neq \beta \neq \gamma \neq 90^{\circ} \quad \alpha \neq \beta \neq \gamma \neq 90^{\circ} \quad \alpha=\beta=\gamma \neq 90^{\circ}\)

The number of atoms per unit cell of BCC structure is (a) 1 (b) 2 (c) 3 (d) 4

In body-centred cubic structure, the length of unit cell edge interms of radius of atom \((r)\) is (a) \(\frac{4}{3} r\) (b) \(\frac{4}{\sqrt{3}} r\) (c) \(\frac{\sqrt{4}}{3} r\) (d) \(\frac{4}{3} \sqrt{r}\)