40. A beam of X-ray consists of equal intensities of wavelengths 0.064 Å and
0.098 Å. When they pass through a piece of lead, their attenuated beam
intensity is in the ratio 3:1. The mass absorption coefficients are 0.164 m
2 /kg
for harder component and 0.35 m
2 /kg for softer component, respectively. If the
density of lead piece is 11340 kg/m
3 , its thickness will be:
(a) 7.22 Â 10
–4 m
(b) 6.22 Â 10
–4 m
(c) 5.22 Â 10
–4 m
(d) 4.22 Â 10
–4 m
41. A copper sheet of 1.05 mm thick can reduce the intensity of the X-ray beam to
7.5% of its original value. If the density of copper sheet is 8930 kg/m
3 , its mass
absorption coefficient will be:
(a) 3.276 m
2 /kg
(b) 2.276 m
2 /kg
(c) 1.276 m
2 /kg
(d) 0.276 m
2 /kg
42. A beam of neutron with energies ranging from zero to several electron volts is
directed at a crystal with interplanar spacing 3.03 Å. In order that the reflected
neutrons have a kinetic energy of 0.1 eV, the angle between the incident beam
and the crystal is:
(a) 8° 36′
(b) 6° 36′
(c) 4° 36′
(d) 2° 36’
43. A neutron beam (with neutron rest mass = 1.67 Â 10
À27 kg) of kinetic energy
0.04 eV is diffracted by the plane (100) of Sylvine crystal ðd 100 ¼ 3:14 ˚
AÞ: The
glancing angle h at which the first-order Bragg’s spectrum is observed will be:
(a) 12.16°
(b) 13.16°
(c) 14.16°
(d) 15.16°
44. The energy (in eV) associated with an electron of wavelength 3 Â 10
À2 m is:
(a) 3.68 Â 10
–15 eV
(b) 2.68 Â 10
–15 eV
(c) 1.68 Â 10
–15 eV
(d) 0.68 Â 10
–15 eV
7.4 Other Diffraction Methods
295