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Questions and Answers
What phenomenon occurs when an incident photon collides with a K-shell electron, resulting in the ejection of the electron?
Which interaction is more likely to occur with low energy photons and elements with high atomic numbers?
What is the K-edge in the context of X-ray interactions?
How does the probability of the photoelectric effect occurring relate to atomic number?
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What is required for pair production to occur?
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Which statement is true about the Compton effect?
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What particles are produced during pair production?
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Which of the following elements has the highest binding energy for a K-shell electron?
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Study Notes
X-ray Interactions with Matter
- X-ray interactions are classified into two categories: photon scattering and photon disappearance.
Photon Scattering
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Compton scattering: Occurs when an x-ray photon collides with a loosely bound electron, usually in the outer shell.
- The electron receives a portion of the photon's energy, resulting in a scattered photon with lower energy traveling in a different direction.
Photon Disappearance
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Photoelectric effect: An incident photon interacts with a tightly bound electron in an inner shell, typically the K-shell, and ejects it from the atom.
- The entire photon's energy is absorbed by the electron, which is then ejected as a photoelectron.
- This creates a vacancy in the inner shell that is filled by an electron from a higher energy level.
- This process releases characteristic x-ray photons with energy equal to the difference between the two energy levels.
- The probability of the photoelectric effect increases significantly when the photon energy is slightly greater than the electron's binding energy, creating a sharp rise in the absorption curve known as a K-edge.
- The photoelectric effect is more likely to occur with low-energy photons and elements with high atomic numbers.
- The probability is directly proportional to the atomic number (Z) cubed (Z³) and inversely proportional to the photon energy cubed (E³).
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Pair production: A very energetic photon interacts with the nucleus, causing the photon to disappear and its energy to transform into matter in the form of an electron and a positron.
- A positron is an antiparticle with the same mass as an electron but a positive charge.
- The minimum photon energy required for pair production is 1.022 MeV, which is the combined rest mass energy of an electron and a positron (2 x 0.511 MeV).
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Positron annihilation: A positron interacts with a free electron, resulting in the annihilation of both particles and the release of two photons, each with an energy of 0.511 MeV, in opposite directions.
- This process conserves energy and momentum.
- Two mass units are converted into energy, resulting in a total energy of 1.022 MeV.
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Description
Test your knowledge on X-ray interactions including photon scattering and disappearance. This quiz covers phenomena such as Compton scattering and the photoelectric effect, detailing how X-rays interact with electrons in various shells. Challenge yourself to understand the energy transformations and implications involved in these processes.
