25. A bcc molybdenum sample was studied with the help of X-ray diffraction using
X-rays of wavelength 1.543 Å. Diffraction from {200} planes was obtained at
2h ¼ 58:618
: Assuming the diffraction to be of first order, the value of lattice
parameter will be:
(a) 3.15 Å
(b) 4.15 Å
(c) 5.15 Å
(d) 6.15 Å
26. X-rays of unknown wavelength are diffracted from an iron sample. First peak
was observed for (110) planes at 2h ¼ 44:70
: If the lattice parameter of bcc
iron is 2.87 Å, the wavelength of the X-ray used is:
(a) 0.543 Å
(b) 1.543 Å
(c) 2.543 Å
(d) 3.543 Å
27. The longest wavelength that can be analyzed by a rock-salt crystal with
interplanar spacing 2.82 Å in the first order of X-ray diffraction is:
(a) 3.64 Å
(b) 4.64 Å
(c) 5.64 Å
(d) 6.64 Å
28. The longest wavelength that can be analysed by a rock-salt crystal with
interplanar spacing 2.82 Å in the second order of X-ray diffraction is:
(a) 5.82 Å
(b) 4.82 Å
(c) 3.82 Å
(d) 2.82 Å
29. The glancing angle on the plane (110) of a cube of rock-salt (a = 2.81 Å)
corresponding to second order maximum for the X-rays of wavelength 0.71 Å
is:
(a) 20.9°
(b) 30.9°
(c) 40.9°
(d) 50.9°
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7 Diffraction of Waves and Particles by Crystal