16. Side of a primitive square unit cell is 2Å. Construct another unit cell of equal
area whose one side is the diagonal of the square. The length of this side is:
(a)
ffiffi ffi
2
p ˚
A
(b)
ffiffi ffi
4
p ˚
A
(c)
ffiffi ffi
6
p ˚
A
(d)
ffiffi ffi
8
p ˚
A
17. Side of a primitive square unit cell is 2Å. Construct another unit cell of equal
area whose one side is the diagonal of the square. The diagonal makes an angle
with x-axis is:
(a) 40°
(b) 45°
(c) 50°
(d) 55°
18. The sides of a primitive rectangle are 3Å and 2Å, respectively. Construct a new
unit cell with the edges defined by the vectors from the origin to the points with
coordinates 1, 0 and 1, 2. Area of the new unit cell is:
(a) 6 Å
2
(b) 8 Å
2
(c) 10 Å
2
(d) 12 Å
2
19. The sides of a primitive rectangle are 3Å and 2Å, respectively. Construct a new
unit cell with the edges defined by the vectors from the origin to the points with
coordinates 1, 0 and 1, 2. The number of lattice points in the new unit cell is:
(a) 4
(b) 3
(c) 2
(d) 1
20. A primitive rectangular unit cell has a = 2Å, b = 3Å, and c = 90°, respectively.
A new unit cell is chosen with the edges defined by the vectors from the origin
to the points with coordinates 2, 0 and 0, 3. Area of the new unit cell is:
(a) 36 Å
2
(b) 27 Å
2
(c) 18 Å
2
(d) 9 Å
2
1.5 Close Packing of Identical Atoms (Spheres)
37