We know that
I = I 0 exp Àl
ð Þx
or
I
I 0
= I 0 exp Àl
ð Þx ¼ 7:5% ¼
7:5
100
¼ 0:075
or exp lx
ð Þ¼
1
0.075
¼ 13.33
or lx = ln 13.33
ð
Þ
or
l ¼
ln 13.33
ð
Þ
x
¼
ln(13:33Þ
1:05 Â 10 À3 ¼ 2466.7m
À1
Further, the mass absorption coefficient is given by
l m ¼
l
q
¼
2466.7
8930
¼ 0.276 m
2 /kg
7.4 Other Diffraction Methods
(i) Neutron Diffraction
Depending upon the energy of the neutron from the pile of a reactor, the wavelength
of a neutron beam is given by
k¼
h
ffiffiffiffiffiffiffiffiffi ffi
2mE
p
¼
0.28
ffiffiffi
E
p
where mass of the neutron, m ¼ 1:675 Â 10
À27 kg:
(ii) Electron Diffraction
Ignoring the relativistic correction, the wavelength associated with the moving
electron beam is given by
k¼
h
ffiffiffiffiffiffiffiffiffi ffi
2mE
p
¼
h
ffiffiffiffiffiffiffiffiffiffiffiffi
2meV
p
¼
12.24
ffiffiffi ffi
V
p
where mass of the neutron, m ¼ 9:1 Â 10
À31 kg:
284
7 Diffraction of Waves and Particles by Crystal