P7: Radioactivity Flashcards
What is radioactive decay
When an unstable nucleus will become more stable over time by spontaneously (random) emitting ionising radiation.
What are the names of substances that decay radioactively
Radioactive substances
What are the three types of ionising radiation
Alpha
Beta
Gamma
What is alpha radiation
A type of radiation produced by alpha decay.
It releases helium nuclei, known as alpha particles
What is beta radiation
Another type of radiation produced by beta decay. It releases electrons known as beta particles
What is gamma radiation
Final type of radiation produced by gamma decay. It is a high electromagnetic energy wave with higher frequencies than X Rays
What is an alpha particle
Helium nuclei
What is a beta particle
Electron
What is a fact about radioactive decay
Unpredictable
We cannot predict when atoms will emit ionising radiation
What are the three ways we can detect radioactivity
Cloud chambers
Photographic film
Geiger counter
What is a cloud chamber
Containers full of air containing alcohol vapour.
Ionising radiation enters the air and leaves a trail of ionised air molecules.
The alcohol vapour condenses on the ionised air molecules, showing the trail of radiation
What is the effect of the photographic film
Ionising radiation shares the same effect with this and light.
A bright spot appears wherever ionising radiation hits the film
What is a geiger counter
Ionising radiation enters a tube of low pressure gas. Atoms in the gas are ionised, knocking electrons out of the atom. Gases then conduct electricity and completes an electric circuit.
When radioactive substances enter a Geiger counter, it makes a clicking noise
What is background radiation
This is when atoms or isotopes are very common, they even exist in our body.
They decay radioactively, meaning we are always surrounded by background radiation
What is the count rate for geiger counters
Number of decays recorded per second
What are sources of background radiation
Foods
Radon gas
Rocks
Sun
What are the properties of an alpha particle
An alpha particle contains 2 protons and 2 neutrons.
This creates a relative mass of 4 for an alpha particle.
Alpha particles are big and heavy so alpha radiation is strongly ionising.
They do lots of damage, but can be stopped by small amounts of matter such as paper
What are the properties of a beta particle
A beta particle is made up of high energy electrons.
Beta radiation is more penetrating than gamma radiation but less ionising than alpha radiation.
It can pass through paper but is stopped by aluminium foil
What are the properties of gamma radiation
Gamma radiation is the least ionising of the three.
It does deal less damage than alpha and beta radiation and cannot be stopped by ANYTHING
How does penetration link to ionising radiation
Strongly ionising radiation is less likely to penetrate materials. It damages materials much more so it comes to a stop soon.