UNIT 1 E
3 marks Questions:
11. What is meant by ‘ Bravai’s
Lattice ’? Write the names
of seven crystal system.
A. In geometry and crystallography, a Bravai’s lattice is an infinite
array of discrete points in three dimensional space generated by a set of
discrete translation operations described by:
When the discrete points are atoms, ions, or polymer strings of solid
matter, the Bravais lattice concept is used to formally define a crystalline
arrangement and its (finite) frontiers. A crystal is made up of a periodic
arrangement of one or more atoms (the basis) repeated at each lattice point.
Consequently, the crystal looks the same when viewed from any equivalent
lattice point, namely those separated by the translation of one unit cell (the
motif).
12. Define space
lattice. What are the characteristics of a
space Lattice?
A. A crystalline substance is one which is made of crystals or parts
of crystals. In a crystal, the atoms are
arranged in a periodic and regular geometric pattern in space. The arrangement
of atoms in a crystal can be described with respect to three dimensional net of
straight lines, called a space Lattice.
13. Explain with neat
sketches the arrangement of
atoms in B.C.C,
F.C.C and H.C.P
Lattice.
A.
BCC
FCC
HCP
14. Explain simple
cubic crystal structure with neat
sketch.
A.
15. Draw the cubic
crystal planes for following Miller
indices:
(i) (0 1
0) (ii) (0 0 1)
(iii) (1 2 0).
A.
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