Chapter 5

In a body-centred cubic arrangement, A ions occupy the centre whil e B ions occupy corners of the cubic. The formula of the solid is. a) ${\mathrm{AB}}_2$ b) $\mathrm{AB}$ c) ${\mathrm{A}}_2\mathrm{B}$ d) None of these

Radius ratio $r_{\mathrm{Na}}+/r_{\mathrm{C}1}^{-}$ in $\mathrm{NaCl}$ crystal is a) $0.524$ b) $0.414$ c) $0.732$ d) $0.80$

The number of atoms per unit cell in simple cubic, face-centred cubic and body-centred cubic are: a) $1,4,2$ b) $4,1,2$ (c) $2,4,1$ (d) 4, 8, 2

Crystals can be classified into (a) 7 systems b) 9 systems c) 10 systems

Close packing is maximum in the crystal lattice of (a) face-centred cubic (b) $\mathrm{BCC}$ (c) simple cubic

Bragg's equation is a) $2\cap \mathrm{\Lambda }=d\sin \theta$ b) $n\lambda =2d\sin \theta$ c) $\frac{n}{\lambda }=d\sin \theta$

In Bragg's equation for diffraction of X-rays, $n$ represents a) number of moles b) quantum number c) order of reflection d) Avogadro number

Total number of planes, axes and centre of symmetries in a crystal is termed as a) elements of symmetry (b) symmetries c) symmetry operations

If in a crystal intercepts are $1,\mathrm{\infty }$ and $\mathrm{\infty }$, the Millar indices are: (a) (100) (b) $(101)$ (c) (110) (d) (000)

Millar indices in a crystal indicate (a) designation of plane crystals (b) intercepts of plane on $\mathrm{X}$ -axis (c) reciprocals of fractional intercepts of that plane on various axes (c) none