Nuclear Radiation Flashcards
What happens to nuclei that are unstable
They break down to become more stable, making them radioactive.
What could instability within a nucleus be caused by
too many neutrons
too few neutrons
too many nucleons (nucleus is too heavy)
too much energy in the nucleus
What is radioactive/nuclear decay
The nucleus decays by releasing energy and/or particles, until it reaches a stable form
What is the nature of radioactive decay
It is random and spontaneous, it can’t be predicted
what is an alpha particle (α) made of
A helium nucleus, 2 protons, 2 neutrons & 2 electrons
What is the relative charge on an alpha particle
+2
What is the mass of an alpha particle
4 u (atomic units)
What is Beta-minus (β−), which is the normal Beta particle, and it’s properties
An electron, -1 charge, negligible mass
What is Beta-plus (β+) particle and it’s properties
A positron, +1 charge, negligible mass
What is gamma particle (γ) and it’s properties
Short-wavelength, high-frequency EM wave (gamma wave). Charge = 0, mass = 0
What can all waves, like gamma, act as
As a particle. You can have gamma photons
What are radioactive emissions known as and why
Ionising radiation because when radiation hits an atom, it can knock off electrons, creating an ion.
How are alpha, beta and gamma radiation tested to see if they penetrate
They are fired at a variety of objects with detectors placed on the other side. If they are detected, that means they have penetrated that object
What is the ionising ability of alpha, beta-minus and gamma radiation
alpha - strong
beta-minus - weak
gamma - very weak
What is the speed of alpha, beta-minus and gamma radiation
alpha - slow
beta-minus - fast
gamma - speed of light
What is the penetration/range of alpha, beta-minus and gamma radiation
alpha - very small, absorbed by paper or a few cm of air
beta-minus - small, absorbed by ~3 mm of aluminium
gamma - very large, absorbed by many cm of lead, or several meters of concrete
Is alpha, beta-minus and gamma radiation affected by magnetic field
Alpha and Beta-minus have a charge, so they are affected by a magnetic field. Gamma is not affected as it has a charge of 0.
Why does beta-plus radiation not have the properties of the others
It is annihilated by an electron, so it has virtually zero range.
How are ionising ability, charge and penetration range related
The more charge the radiation has, the more ionising ability it has. A particle with high ionising ability will have a low penetration range.
How are ionising ability, charge and penetration range related in alpha radiation
Alpha particles are strongly positive, +2 charge, so they can easily pull electrons off atoms, ionising them. Ionizing an atom transfers some of the energy from the alpha particle to the atom (you are pulling off an electron which takes energy). The alpha particle quickly ionises many atoms (about 10,000 ionizations per alpha particle) and loses its energy, meaning alpha particles don’t travel very far, they have low penetration.
How are ionising ability, charge and penetration range related in beta-minus radiation
Beta-minus particles have lower mass and charge than alpha particles, but a higher speed, so they also have a significant amount of energy. This means they can still knock off electrons from atoms. Each beta-particle will ionise about 100 atoms, losing energy at each ionisation. Since beta-minus has lower number of ionisations than alpha radiation , it travels further than alpha radiation, meaning it has higher penetration
How are ionising ability, charge and penetration range related in gamma radiation
Gamma radiation is even more weakly ionising than beta-minus as it has 0 charge and 0 mass. This means it has very high penetration, as it has a lot of energy for traveling/penetrating since it isn’t losing it by ionising a bunch of atoms
What must you do when you take a reading from a radioactive source (CORE PRAC ADVICE)
You need to measure the background radiation separately and subtract it from your measurement
What are the sources of background radiation
The air: Radioactive radon gas released from rocks. It emits alpha radiation. The concentration of this gas in the atmosphere varies a lot from place to place, but it’s usually the largest contributor to background radiation.
The ground and buildings: all rock contains radioactive isotopes
Cosmic radiation: Cosmic rays are particles (mostly high-energy protons) from space. When they collide with particles in the upper atmosphere, they produce nuclear radiation
Living things: All plants and animals contain carbon, and some of this will be the radioactive isotope carbon-14
Man-made radiation: In most areas, radiation from medical or industrial sources make up a tiny, tiny fraction of the background radiation.