228
Problem
53. What are the mechanisms by which energy is transferred to the material irradiated by electromagnetic radiations of different energies? Distinguish among the
linear, mass, and atomic absorption coefficient of an electromagnetic radiation
in matter.
54. What is Compton scattering? How does the cross-section for the process depend
on the nature of the material and the energy of the photons?
55. What aspects of the interaction of electromagnetic radiation with matter have
led to the development of the scintillation counter. Discuss.
56. (a) Distinguish between the modes of interaction of α-particles and γ -rays with
matter. How do these interactions help in detecting these radiations?
(b) γ -radiations of 1 MeV undergo Compton scattering in a material. Calculate the maximum energy loss in the radiation in a single interaction if the
Compton wavelength is 0.024
◦ A. What would be the condition when there
is no loss of energy by Compton scattering?
57. (a) Describe the processes by which γ -radiation loses its energy while passing
through the matter.
(b) Given the half-thickness value for water for γ -rays emitted by
60 Co as 11 cm,
calculate the mass absorption coefficient of water. Calculate the thickness
of water that would be required to reduce the intensity of a 1000 Ci source
of
60 Co by a factor of 10. (Density of water is 0.998 g cm
−2 .)
58. Explain the principle of a proportional counter and compare its merit with that
of the liquid scintillation counter.
59. What are the different types of ionization counters? Explain the applications and
limitations of these detectors.
60. (a) Describe the design and operation of a scintillation counter. Explain how is
it used for measuring β-particles and γ -radiations.
(b) A counting system has a resolving time of 150 ms. The observed count rate
is 10,109 cpm. Calculate the true count rate.
61. Find out the decay scheme of
90 Sr. A sample of freshly prepared
90 Sr is given
to you. Would you prefer to count the sample after 10–12 days of separation
or immediately after the separation to get the best efficiency in counting? Give
reasons for your answer.
62. Find out the decay scheme of
111 Ag. Which counter would you use to count
this isotope to get a good efficiency of counting? Give the theory of the counter
selected by you.
63. What modification (i.e., coincidence or anti-coincidence) would you like to do
with your selected counter to increase the efficiency of the counting and why?
64. Describe the design and the operation of a scintillation spectrometer. Explain
how it is used for measuring α-particles, β-particles, and γ -rays.
65. A counting system has a resolving time of 500 ms. The observed counting rate
is 1250 cpm. Calculate the true counting rate and coincidence error.
66. What are the essential differences (i) between an ionization chamber and a
counter and (ii) between a proportional counter and a Geiger–Müller counter?
67. Explain the principles of the scintillation counter and its use for measuring αparticles, β-particles of energy 1.58 MeV, and γ -rays of 1.2 MeV.
Problem
53. What are the mechanisms by which energy is transferred to the material irradiated by electromagnetic radiations of different energies? Distinguish among the
linear, mass, and atomic absorption coefficient of an electromagnetic radiation
in matter.
54. What is Compton scattering? How does the cross-section for the process depend
on the nature of the material and the energy of the photons?
55. What aspects of the interaction of electromagnetic radiation with matter have
led to the development of the scintillation counter. Discuss.
56. (a) Distinguish between the modes of interaction of α-particles and γ -rays with
matter. How do these interactions help in detecting these radiations?
(b) γ -radiations of 1 MeV undergo Compton scattering in a material. Calculate the maximum energy loss in the radiation in a single interaction if the
Compton wavelength is 0.024
◦ A. What would be the condition when there
is no loss of energy by Compton scattering?
57. (a) Describe the processes by which γ -radiation loses its energy while passing
through the matter.
(b) Given the half-thickness value for water for γ -rays emitted by
60 Co as 11 cm,
calculate the mass absorption coefficient of water. Calculate the thickness
of water that would be required to reduce the intensity of a 1000 Ci source
of
60 Co by a factor of 10. (Density of water is 0.998 g cm
−2 .)
58. Explain the principle of a proportional counter and compare its merit with that
of the liquid scintillation counter.
59. What are the different types of ionization counters? Explain the applications and
limitations of these detectors.
60. (a) Describe the design and operation of a scintillation counter. Explain how is
it used for measuring β-particles and γ -radiations.
(b) A counting system has a resolving time of 150 ms. The observed count rate
is 10,109 cpm. Calculate the true count rate.
61. Find out the decay scheme of
90 Sr. A sample of freshly prepared
90 Sr is given
to you. Would you prefer to count the sample after 10–12 days of separation
or immediately after the separation to get the best efficiency in counting? Give
reasons for your answer.
62. Find out the decay scheme of
111 Ag. Which counter would you use to count
this isotope to get a good efficiency of counting? Give the theory of the counter
selected by you.
63. What modification (i.e., coincidence or anti-coincidence) would you like to do
with your selected counter to increase the efficiency of the counting and why?
64. Describe the design and the operation of a scintillation spectrometer. Explain
how it is used for measuring α-particles, β-particles, and γ -rays.
65. A counting system has a resolving time of 500 ms. The observed counting rate
is 1250 cpm. Calculate the true counting rate and coincidence error.
66. What are the essential differences (i) between an ionization chamber and a
counter and (ii) between a proportional counter and a Geiger–Müller counter?
67. Explain the principles of the scintillation counter and its use for measuring αparticles, β-particles of energy 1.58 MeV, and γ -rays of 1.2 MeV.