Question

Chapter 31/32 Part 2

1. The energy of 28.3 keV is required to ionize a molecule of the gas inside a Geiger tube, thereby producing an ion pair. Suppose a particle of ionizing radiation deposits 0.475 MeV of energy in this Geiger tube. What maximum number of ion pairs can it create?

2. Calculate the energy in MeV released in a ? decay of ²⁴⁹Cf. Assume that the masses of ²⁴⁹Cf and ²⁴⁵Cm are 249.075573 and 245.057087 u, respectively.

3. Calculate the number of grams of deuterium in an 38,000 L swimming pool, given deuterium is 0.0123% of natural hydrogen. Assume that the density of water is 1 kg/L.

4. Calculate the energy in MeV released in an electron capture by ¹⁵O. Assume that the masses of ¹⁵O and ¹⁵N are 15.003087 and 15.000076 u, respectively.

Answer 1

1 )

E_o = energy required per a pair is 28.3 eV

E_total = 0.475 MeV = 0.475 X 10⁶ eV

E_total = n E_o

0.475 X 10⁶ = n X 28.3

n = 16784.45

2 )

using equaiton

E = ( m_i - m_f - m_p )C²

E = ( 249.075573 - 245.057087 - 4.0012 ) C²

E = 0.017286 uC²

1 u C² = 931.5 MeV

0.017286 ue² = 0.017286 X 931.5

= 16.1012 MeV

3 )

the amount is

38000 X ( 1000 / 1 ) X ( 2.02 / 18 ) X ( 0.0123 / 100 )

= 524.523 g² H

4 )

Q = ( 15.003087 - 15.0000760 ) u C²

Q = 0.003011 u C²

1 u C² = 931.5 MeV

Q = 0.003011 X 931.5

Q = 2.8 MeV