25. The linear atomic density (i.e., the number of atoms/m) along [111] in bcc iron
whose lattice parameter a = 2.87 Å:
(a) 4.02 Â 10
9
(b) 3.02 Â 10
9
(c) 2.02 Â 10
9
(d) 1.02 Â 10
9
26. The planar atomic density (i.e., the number of atoms/area) of the centered
square lattice with a = 4
ffiffi ffi
2
p Å is:
(a) 5.25 Â 10
18
(b) 6.25 Â 10
18
(c) 7.25 Â 10
18
(d) 8.25 Â 10
18
27. The atomic density (i.e., the number of atoms/area) in (100) plane of a simple
cubic structure with a = 2.5 Å is:
(a) 4.60 Â 10
19
(b) 3.60 Â 10
19
(c) 2.60 Â 10
19
(d) 1.60 Â 10
19
28. The atomic density (i.e., the number of atoms/area) in (110) plane of a simple
cubic structure with a = 2.5 Å is:
(a) 4.13 Â 10
19
(b) 3.13 Â 10
19
(c) 2.13 Â 10
19
(d) 1.13 Â 10
19
29. The atomic density (i.e., the number of atoms/area) in (111) plane of a simple
cubic structure with a = 2.5 Å is:
(a) 9.24 Â 10
18
(b) 8.24 Â 10
18
(c) 7.24 Â 10
18
(d) 6.24 Â 10
18
30. The atomic density (i.e., the number of atoms/area) in (100) plane of a bcc iron
with a = 2.87 Å is:
(a) 1.21 Â 10
19
(b) 2.21 Â 10
19
(c) 3.21 Â 10
19
(d) 4.21 Â 10
19
132
3 Unit Cell Calculations