Question

A monochromatic light beam of wavelength 0.1790 nm is incident on BCC iron crystal lattice, with lattice parameter 0.2866 nm. Assume that the order
of reflection is 1. The diffraction angle θ, rounded to the nearest integer for the (220) set of planes is 124 degrees

Answer 1

 Polymorphous or Allotropic Material: Same Material with two or more

different crystal structures.

 Crystal Structure may vary with temperature or pressure ( Allotropy

/polymorphism)

 Examples: (1) Titanium: α, β-Ti. (2) Carbon: diamond, graphite. (3) Iron.

Anisotropy: properties to be different in different directions.

Isotropy: measured properties are independent of directions, or same properties

in different directions

X-rays are produced whenever high-speed electrons collide with a metal

target. A source of electrons – hot W filament, a high accelerating voltage between

the cathode (W) and the anode and a metal target, Cu, Al, Mo, Mg. The anode is a

water-cooled block of Cu containing desired target metal.

 X-ray diffraction is used for crystal structure and interplanar spacing

determinations.