RADIATION Flashcards
What is alpha radiation?
Radiation in particle form with energy typically 2-5 meV
What are gamma rays?
Electromagnetic radiation with energy typically 1-100 MeV
What is visible light?
Electromagnetic radiation with wavelength typically 400-700nm
What are x-rays?
Electromagnetic radiation with photon energy typically 3-100 keV
What does A (mass number) represent?
Total number of nucleons- protons plus neutrons
Which medium block alpha particles?
Paper
Which medium blocks beta particles?
PLastic
Which medium blocks gamma x ray particles?
Lead
Which medium blocks gamma decay rays?
Concrete
What happens to the intensity with distance?
As distance increases, intensity decreases
What is alpha radiation?
alpha rays that are positively charges and a nucleus emits an alpha particle if nuclei are too heavy. Loses two protons and two neutrons (A-4, Z-2). Undergoes transmutation (changing elements after one decay)
Why does alhpa radiation occur?
Occurs because the strong nuclear force can’t hold very large nuclei together- only a short range force and only acts between neighbouring nucleons.
What are the two types of beta particle radiation?
Beta plus and beta minus
What occurs in beta plus radiation and when does it occur?
When there are more protons than the neutrons and it is decay from a positron emission (e+) rather an electron emission. LOSES one proton (positron) (Z-1)
What occurs in beta minus radiation and when does it occur?
When there are more neutrons than protons and neutron forms a proton, electron and an antineutrino. GAINS one proton (Z+1). Daughter nucleus charge is 1 electron greater than parent. (electron is from within the nucleus!!!) Excess neutron turns into a proton and electron. Electron ejected energetically.
What is the difference between gamma rays and x-rays?
How they are produced. Gamma rays are from the nucleus of radionucleide after radioactive decay, X-rays are produced when electrons strike a target or when electrons are rearranged wihthin an atom .
What is the typical energy range for gamma rays?
more than 100 keV
What is the typical energy range for x-rays
100eV to 100 000 eV
What is gamma radiation?
High energy photons. Nucleus can be in excited state and when going to ground state can emitphotons- gamma rays- always has the same energy. Gamma rays have no charge so TRANSMUTATION (changing of elements)
What can be the cause of gamma radiation?
Violent collision with another particle or nucleus may be in excited state after previous radioactive decay
What is electron capture?
Nucleus absorbs one of its orbiting electrons (usually from innermost K shell) and electron dissappears and proton in nucleus then becomes a NEUTRON
What is the breaking radiation?
smooth continuous part of the curve. Electron passes through nucleus (tungsten) then slows down due to the pull of nucleus . It loses kinetic energy from this and is given off as a photon (from interaction with electric field )-frequency of photon is in x-ray range
What is characteristic x-rays?
COMPLETELY DIFFERENT way of making x-rays
Electron will be an incident electron and ionise one of the tungsten atoms
will ionise from the lowest shell (K shell ground state) Will eneter K shell (incident electron) then knock an electron out and both the incident electron and knocked out electron will go in different directions.
This leaves empty space and then electron from outer shell will fill lower shell. DIfference in energy levels is the photon energy given off.
In breaking radiation, what type of K radiation will occur from L shell electron –> K shell?
K alpha radiation
In breaking radiation, what type of K radiation will occur from M shell to L shell?
K beta radiation
What does dose depend on?
Energy absorbed by body
- type of radiation
- how tissues react to radiation
What is absorbed dose?
The energy of ionising radiation deposited in 1 kg of material - meadured in Grays (1J/kg)
What is dosimetry?
amount of radiation dose and its effect
What is equivalent dose?
Takes into account the type of radiation and its energy using radiation weighting factor Wr (measured in Sieverts)
What is effective dose?
takes into account the biological effect on the different organs by using the organ weighting factor Wt. (also measured in Siverts)
What does Effective dose =
Effective dose= equivalent dose * Wt (organ weighting factor)
