16. In a diffraction experiment, only one peak is observed in an fcc material at
2h ¼ 121
when an X-ray of wavelength 1.54 Å is used. The possible reflection
is:
(a) (111)
(b) (200)
(c) (220)
(d) (222)
17. The Bragg’s angle corresponding to a reflection for which h
2
þ k
2
þ l
2
ð
Þ¼8 is
found to be 14.35°. If the X-ray of wavelength 0.71 Å is used, the lattice
parameter of the crystal is:
(a) 3.05 Å
(b) 4.05 Å
(c) 5.05 Å
(d) 6.05 Å
18. The Bragg’s angle corresponding to a reflection for which h
2 + k
2 + l
2
À
Á
¼ 8
is found to be 14.35°. The X-ray of the wavelength 0.71 Å is used. If there are
two other reflections of smaller Bragg’s angles, the crystal structure of the
sample is:
(a) SC
(b) BCC
(c) FCC
(d) DC
19. When a monochromatic X-ray of wavelength 1.79 Å is used to study the fcc
aluminum powder sample with a camera of radius 57.3 mm, the angle at which
the first reflection to occur is:
(a) 55.5°
(b) 44.5°
(c) 33.5°
(d) 22.5°
20. The first reflection using CuKa radiation from a sample of copper powder
(fcc) has an S-value of 86.7 mm. The camera radius is found to be:
(a) 28.65 mm
(b) 57.3 mm
(c) 85.95 mm
(d) 114.6 mm
9.1 Steps in Crystal Structure Determinations
373