For a crystal,the first-order Bragg reflection of $X$-rays with a wavelength of $2.29 \times 10^{-10} \ m$ occurs at an angle of $27^\circ 8'$. Calculate the distance between two parallel planes.

The density of $Na$ is $0.613 \ g \ cm^{-3}$. If the edge length of the unit cell of $Na$ is $5 \ \mathring{A}$,the effective number of atoms of $Na$ per unit cell is (Atomic weight of $Na = 23 \ u$)

If the density of a gold $(Au)$ crystal crystallizing in a $ccp$ structure is $19.3 \, g/cm^3$,what will be the radius of the atom? (Given: $Au = 197 \, amu$)

An element with atomic mass $100$ has a $bcc$ structure and edge length $400 \, pm$. The density of the element is .............. $g \, cm^{-3}$.

Calculate the number of atoms in $1 \ g$ of a metal if it forms an $fcc$ crystal structure,given that $\varrho \times a^3 = 1.728 \times 10^{-22} \ g$.

If the angle of incidence of $X$-ray of wavelength $3 \mathring{A}$ which produces a second order diffracted beam from the $(100)$ planes in a simple cubic lattice with interlayer spacing $a = 6 \mathring{A}$ is $30^{\circ}$,the angle of incidence that produces a first order diffracted beam from the $(200)$ planes is $.... \, ^{\circ}$