Unit 1.2 Flashcards
List the characteristics of Alpha Radiation.
Emitted from Nucleus Essentially He Nucleus Large Mass (4amu) \+2 charge Mono energetic Travels at 1/20th speed of light. Least penetrating. Range in air is cm, in tissue is mm. High internal hazard.
Describe the interaction of alpha radiation with matter.
Travel in a linear path, created direct ionization and excitation interactions, and rapidly give/lose energy to encountered particles.
List the characteristics of beta radiation.
Emitted from the nucleus Essentially an energetic electron Mass of 1/1836 Mostly Internal Hazard Can be + or neg charge. Emitted in a spectrum of energies. More penetrating than alpha.
Describe the interaction of beta radiation with matter.
Can utilize ionization, excitation, and bremsstrahlung reactions to expend energy. Travel at speed of light. Travel in a tortuous path due to interactions.
What type of shielding should you use for Beta radiation?
Something resembling water (low Z) to minimize bremsstrahlung.
State the origin of gamma rays
When a proton or neutron drops from a higher energy to a lower energy state, the difference is released as an x-ray.
List the properties of photons.
Have energy and momentum, no mass, no charge, travel at speed of light.
State the origin of X-rays; what are the two types?
Emitted from electron cloud.
Characteristic and Bremmstrahlung.
Describe Characteristic X-rays.
Emitted from the nucleus after an electron drops from a higher to a lower energy state and less binding energy is required to hold that electron. These are specific to individual elements.
Describe Bremsstrahlung X-rays.
X-rays released after radial acceleration that occurred due to electrostatic forces.
What are the three ways photons can interact with matter.
Photo-electric Effects
Compton Scattering
Pair Production
What is the Photoelectric Effect?
When a photon transfers energy to a low orbital electron and the electron is released as a photoelectron. Its energy is the energy of the incident photon minus the binding energy of that electron.
What is Compton Scattering?
When a photon transfers energy to a high orbital electron and ‘bounces off’ transferring some energy to the electron and causing it to be released. Photons that do this continue to do so until they have so little energy that they can only undergo photoelectric absorption.
What is Pair Production?
A high-energy ( > 1.022MeV) photon interacts with the nucleus and transfers its energy resulting in a negative and a positively charged electron to be released.
Describe an annihilation reaction.
A positron released by pair production interacts with an electron and the two are mutually destroyed, creating two gamma rays of equal and opposite energy of 0.511MeV.
