X-RAY DIFFRACTION OR X-RAY CRYSTALLOGRAPHY and MCQ for GPAT, NET JRF exam

X-RAY DIFFRACTION THEORY :-

X-RAY wavelength = 10-2-10nm (10-104pm)

X-ray diffraction is a science of determing arrangements of atoms within the crystals in which beam of X-ray is scattered by atom in the crystal.

X-ray crystallography is based upon transition of inner shell e

Whenever a fast moving eimpings on an atom it may knockout an e completely from one of the inner shells of that atom.

Following the loss of inner shell e one of the outer e– will fall into the vacant orbital with the simultaneous emission of X-ray photon.

The energy of this X-ray photons is equal to difference in the energy between 2 levels involved.

K-series :- if k shell loses  e then e– will fall from higher energy level if it fall from L then it is called as kα series.& if it falls from M then it is called kβ series and so on.

L-series :- if L-shell loses  e then if  e will from M then it is called as Lα series if from N then Lβ series.

If an incident X-ray beam encounters a crystal lattice, general scattering occurs. Althrough most scattering in occurs.Althrough most scattering interferes with itself and is eliminated (destructive interference) diffraction occurs when scattering in a certain direction is in phase with scattered ray from other atomic planes.

Under this conditions the reflections combine to form  new  enhanced wave fronts that mutually reinforce each other The relation by which diffraction occurs is known as the bragg law or equation. Because each crystalline material has a characteristic atomic structure,it will diffract X-ray in a unique characteristic pattern.

BRAGG`S  equations is  nλ=2d

Where,

  • n= order of diffraction
  • λ = wave length
  • = glancing angle
0 30 45 60 90
sinθ 0 1/2 1 1/√2 1

BRAGG`S  equations give the relationship between :-

  • Wave length of x-ray
  • Interplanner distance in crystal
  • Angle of reflection

Q.1 the utilized reflecting plane of a sodium fluoride (NaF) analyzing crystal has a inter planner distance of 1.5 A calculate the wavelength of the 2nd  order diffracted line which has a glancing angle of 45

Answer.   In this questions we give data about n=2,d=1.5 A  and

Here apply bagg law :-  nλ=2d

2×λ=2×1.5× 1.41

λ= 1.05

MCQ :-

1. the utilized reflecting plane of a sodium fluoride (NaF) analyzing crystal has a inter planner distance of 1.5 A calculate the wavelength of the 2nd  order diffracted line which has a glancing angle of 45

a.1.02

b.3.21

c.2.16

d.1.2

2.X-RAY wave length

a. 100-2-10nm

b. 1-2-10nm

c. 10-2-10nm

d. 102-10nm

3. sin45=

a.1/√2

b.1/2

c.0

d.1

4. How to produced x-ray ?

a. By heating electron by uv radiation.

b. Knocking only e-

c. Loss of inner shell e one of the outer e– will fall into the vacant orbital with the simultaneous emission of X-ray photon

d.None of the above.

5.Bragg equation is

a.  nλ=2

b.  n=2d

c.  nλ=2d

d.  nλ=2f

Answer key :-

1.c

2.c

3.d

4.c

5.c

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