PHYS 3330 Module 7 Self Assessment Practice Problems

Module 7 Self Assessment Practice Problems

7.1
K- and L-shell binding energies for cesium are 28 keV and 5 keV, respectively. What are the kinetic energies of photoelectrons released from the K and L shells as 30 keV photons interact with cesium?
Answer: 2 keV, 25 keV
7.2
Estimate the binding energy of electrons in magnesium, given that the wavelength of 337 nm is the longest wavelength that a photon may have to eject a photoelectron from magnesium photoelectrode.
Answer: 3.68 eV
7.3
The cutoff wavelength for the photoelectric effect in a certain metal is 254 nm.
(a) What is the binding energy for that metal?
(b) Will the photoelectric effect be observed for ๐œ† > 254 nm or for ๐œ† < 254 nm? Explain.
Answer: (a) 4.89 eV (b) ๐œ† < 254 nm
7.4
(a) Compute the energy of a photon scattered at 45ยฐ during a Compton interaction, if the energy of the incident photon is 150 keV.
(b) What is the kinetic energy of the Compton electron?
(c) Is the energy of the scattered photon increased or decreased if the photon scattering angle is increased to more than 45ยฐ?
Answer: (a) 138 keV (b) 12 keV (c) decreased
7.5
Incident photons of energy 11.32 keV are Compton scattered, and the scattered beam is observed at 62.9ยฐ relative to the incident beam. 
(a) What is the energy of the scattered photons at that angle?
(a) What is the energy of the scattered electrons at that angle?
Answer: (a) 11.19 keV (b) 0.13 keV
7.6
A photon with wavelength of 0.1110 nm collides with a free electron that is initially at rest. After the collision the wavelength is 0.1135 nm.
(a) What is the kinetic energy of the electron after the collision?
(b) What is its speed?
(c) If the electron is suddenly stopped (for example, in a solid target), all of its kinetic energy is used to create a photon. What is the wavelength of this photon?
Answer: (a) 246 eV (b) 9.3 x 106 m/s (c) 5.04 nm
7.7
A ๐›พ ray of 2.75 MeV from 24Na undergoes pair production in a lead shield. The negative and positive electrons possess equal kinetic energy. What is their kinetic energy? 
Answer: 0.864 MeV each
7.8
A 9.5 MeV photon passes by the nucleus of a lead atom. How many pair productions can take place? Explain.
Answer: 9
7.9
The figure below shows the mass attenuation coefficient for gamma rays and x rays in tungsten.  The black line is the total attenuation coefficient, and each of the colored lines is the contribution to the attenuation coefficient due to each of the different ways that the gamma rays and x rays interact with matter. 
(a) What are the three main ways that gamma rays and x rays interact with matter? 
(b) On the figure, label which interaction type is the source of each of the green, blue and red lines.
Answer:
7.10
Describe the factors that determine if photoelectric or Compton is the most predominant type of interaction.
Answer: