144 Chapter 2. Interaction of Radiation with Matter
the angle of the scattered electron.15.An incident photon having an initial energy of 1.2MeV undergoes Comp-
ton scattering. Estimate the energies of the scattered electrons if the photon
scatters at 30^0 ,60^0 and 90^0.16.A 190keV photon strikes an electron and scatters it off at an energy of 70
keV. Compute the energy and the angle of the scattered photon.17.Determine the thickness of lead required to decrease the intensity of x-rays by
afactorof10^5.18.Compute the mean free paths of 190keVx-ray photons in lead.
19.In a Rutherford scattering experiment 1. 2 × 104 αparticles are detected per
second at an angle of 35^0 with respect to their initial direction of motion. How
manyα-particles one should expect to observe at angles of 15^0 and 90^0?20.Compute the stopping power of 6.5MeV α-particles in air.
21.Compare the range of 2.5MeVprotons andα-particles in air.22.Calculate the mean free path of thermal neutrons in cadmium having a density
of 8. 6 × 103 kgm−^3. The cross section of neutrons can be taken to be 2. 4 × 104
b. Estimate the thickness of cadmium needed to remove 99% of the neutrons
from the beam.23.A gas filled ionization chamber is constructed as shown in the figure below.
The chamber is divided into two 1cmwide regions filled withCO 2 under
standard conditions. The central electrode and the windows are made up of 10
μmmylar foil. The windows are metalized only on their inner sides with 3μm
thick aluminum while the central electrode has 3μmof aluminum deposited
on both sides. Compute the percentage of the number of 100keVphotons that
pass through the chamber without getting absorbed. Mylar can be assumed to
be made up of carbon with a density of 1.4g/cm^3.CO 2 CO 2InsulatorAluminumMylar