Question

X-rays are used for the determination of crystal structure because:

• A. They can travel in a vacuum
• B. They are radioactive
• C. Their wavelength is of the same order as interplanar spacing in crystals
• D. Their speed changes with the change of medium

Hint:

X-rays used for structural analysis have wavelengths that are of the same order as atomic distances in the crystalline solids. This makes them suitable to study the interatomic distances. XRD patterns can also tell us about the different crystalline phases and the defects present in the crystalline lattice.

Answer 1

The Correct Option is C

X-rays are perfectly suited for crystal structure analysis due to their wavelengths (0.1–10 nm) corresponding to crystal lattice interplanar spacing. This characteristic facilitates constructive interference as X-rays interact with crystal atoms, in accordance with Bragg's law:
\(n\lambda = 2d \sin \theta\)
where:
$n$: Order of diffraction.
$\lambda$: Wavelength of X-rays.
$d$: Interplanar spacing.
$\theta$: Angle of incidence.
The resulting diffraction pattern is then examined to identify the crystal's atomic arrangement and symmetry.