Q. To get n-type doped semiconductor, the impurity to be added to silicon should have the following number of valence electrons ?
(a) 2
(b) 5
(c) 3
(d) 1
(ans:-) (b)
Q. How many unit cells are present in a cube shaped ideal crystal of NaCl of mass 1.0 g ? :
(a) 5.14 X 1021
(b) 1.28 X 1021
(c) 1.71 X 1021
(d) 2.57 X 1021
(ans:-)(d)
Q. The crystal system of a compound with unit cell dimensions, a = 0.387, b = 0.387 and c = 0.504 nm and α = β= 90° and γ = 120° is :
(a) cubic
(b) hexagonal
(c) orthorhombic
(d) rhombohedral
(ans:-) (b)
Q. If Z is the number of atoms in the unit cell that represents the closest packing sequence ABCABC......., the number of tetrahedral voids in the unit cell is equal to :
(a) Z
(b) 2Z
(c) Z/2
(d) Z/4
(ans:-) (b)
Q. The appearance of colour in solid alkali metal halides is generally due to :