PHYS 3330 Module 8 Self Assessment Practice Problems

Module 8 Self Assessment Practice Problems

8.1
What is the ratio of the number of interactions that a 20 MeV electron undergoes in coming to rest compared to a 6 MeV electron?
Answer: 3.4
8.2
Electrons with a kinetic energy of 1.0 MeV have an SI in air of about 60 IP/cm. Estimate the stopping power of these electrons in air.
Answer: 2.04 keV
8.3
Alpha particles of 2.0 MeV have an LET in air of 0.175 keV/𝜇m. What is the SI of these particles in air if W/e is assumed to be 33.97 eV/IP?
Answer: 51520 IP/cm
8.4
Approximately how far does a 6 MeV electron travel in water? A 20 MeV electron?
Answer: 3 cm, 10 cm
8.5
What is the ratio of radiative energy loss to collisional energy loss for a 6 MeV electron in water? A 20 MeV electron? Note, the effective atomic number of water is approximately 7.4.
Answer: 0.054, 0.180
8.6
Describe the process of charged particle interactions that play a role in collision stopping power.
Answer:
8.7
A proton of kinetic energy 2.5 GeV passes through a sheet of lead 15 mm thick. The density of lead is 11.4 × 103 kg/m3. Use the graph below to estimate the energy lost by the proton.
Answer: ~24 MeV
8.8
Explain why bremsstrahlung is a more important energy loss mechanism for electrons than for protons travelling through matter.  Explain why energy loss rate by bremsstrahlung is greater for electrons travelling through lead than for electrons travelling through water.
Answer:
8.9
An alpha particle, a proton and a beta particle are incident on a thick iron shield. All have the same kinetic energy. Which particle penetrates the greatest distance into the iron and which penetrates the least?
Answer:
8.10
(There are only 9 problems in this self-assessment.)
Answer: