7.2 Problems 391
7.83 Calculate the spread in energy of the 661 keV internal conversion line of^137 Cs
due to the thermal motion of the source. Assume that all atoms move with the
root mean square velocity for a temperature of 15◦C.
[Osmania University]
7.84 Pound and Rebeka at Harward performed an experiment to verify the Red shift
predicted by general theory of Relativity. The experiment consisted of the use
of 14 keVγ-ray^57 Fe source placed on the top of a tower 22.6 m high and the
absorber at the bottom. The red shift was detected by the Mosbauer technique.
What velocity of the absorber foil was required to compensate the red shift,
and in which direction?
7.2.9 Radioactivity (General) .........................
7.85 The disintegration rate of a radioactive source was measured at intervals of
four minutes. The rate was found to be (in arbitrary units) 18.59, 13.27,
10.68, 9.34, 8.55, 8.03, 7.63, 7.30, 6.99, 6.71, and 6.44. Assuming that the
source contained only one or two types of radio nucleus, calculate the half
lives involved.
[University of Durham]
7.86 100 millicuries of radon which emits 5.5 MeVα-particles are contained in
a glass capillary tube 5 cm long with internal and external diameters 2 and
6 mm respectively. Neglecting end effects and assuming that the inside of the
tube is uniformly irradicated by the particles which are stopped at the surface,
calculate the temperature difference between the walls of a tube when steady
thermal conditions have been reached.
Thermal conductivity of glass= 0 .025 Cal cm−^2 s−^1 C−^1
Curie= 3. 7 × 1010 disintegrations per second
J= 4 .18 joule Cal−^1
[University of Durham]
7.87 Radium being a member of the uranium series occurs in uranium ores. If the
half lives of uranium and radium are respectively 4. 5 × 109 and 1,620 years,
calculate the relative proportions of these elements in a uranium ore, which
has attained equilibrium and from which none of the radioactive products
have escaped.
[University of Durham]
7.88 A sealed box was found which stated to have contained an alloy composed of
equal parts by weight of two metals A and B. These metals are radioactive,
with half lives of 12 years and 18 years, respectively and when the container
was opened it was found to contain 0.53 kg of A and 2.20 kg of B. Deduce
the age of the alloy.
[University of New Castle]