Crystals MCQ Level – 1 - Physics MCQ

CsCl shows a body centred cubic lattice with a coordination number 8 for each ion. 
 

Correct Answer :- b

Explanation : Bragg reflection or diffraction occurs when light waves are incident on an ultrasonic wave with a comparable wavelength. The light is reflected in a specular fashion by the ultrasonic grating, and undergoes constructive interference in accordance with Bragg's law.

 Let  be the scattered wave vector, then from Ewald construction :

K' = K - G....(i)

Since, for elastic scattering, there will be no change in the magnitude of the vector i.e.

|K| = K' = 2pi/λ

Now squaring (i),

K² = K² + G² - 2K . G

G² = 2K . G

packing fraction of simple cubic = 52% packing fraction of bee = 68%
packing fraction of fee = 74%
packing fraction of diamond = 34%
The correct answer is: diamond

For bcc structure ,


 The correct answer is: 

Primitive translation Vectors of simple cubic lattice may be written as :

Then primitive translation vector of reciprocal lattice is



Hence, the reciprocal lattice is itself a simple cubic lattice with lattice constant 

The correct answer is: simple cubic

from figure, AB = a

The correct answer is:

The correct option is D

The primitive translation vector of the reciprocal lattice to the above lattice be calculated as :

b₁=(2π/a)(-i+j+k);

b₂=(2π/a)(i-j+k);

b₃=(2π/a)(i+j-k);

volume of the reciprocal lattice is:

=(2π/a)³[(-i+j+k) (i-j+k)]

=4(2π/a)³

The correct answer is, 4(2π/a)³

Nearest neighbour to an atom (say at origin) is the atom present is the centre of the
at point P and the position of P can be =

The correct answer is: = 

Here AC is the nearest distance while AB or AD forms the nearest neighbour distance which is equal to ' a '.
The correct answer is: a