Paper 1 - Ionising Radiation Flashcards
When do radioactive substances decay ?
The nucleus of a radioactive substance is unstable, meaning it can easily change or decay. When decay occurs radiation is emitted which causes the nucleus to lose energy and become stable.
How can we predict radioactive decay ?
You cannot predict when a nucleus will decay- it is a random process
What are alpha particles?
Alpha particles contain two protons and two neutrons, like the nucleus of a helium atom. They have a relative mass of 4, no electrons so charge of 2+ (Written as He or directly proportional symbol)
What are beta particles
Beta particles are high energy, high speed electrons ■ the electrons that are beta particles come from the nuclei of atoms when a neutron transforms into a proton. Beta particles do not ionise the atoms as they leave them ■
They have a relative mass of an electron and same charge as electron. Written as b with a tail minus or e written as an element with 0 on the top and -1 on the bottom
What are positions
High energy, high speed electrons with the same mass of electrons but a positive charge. Written oppositly to beta particles.
What are gamma rays
Written as Y with the left arc curved downwards. They are high frequency EM waves - travel at the speed of light. They do not have a charge.
Neutrons role in decay. (Mass and charge also)
Neutrons can also be emitted from an unstable nucleus, having a mass of 1 and a neutral charge.
Properties of radiation.
Ionising radiation can penetrate through all materials.
Properties of alpha and gamma
Alpha and gamma rays collide can collide with atoms, ionising them and causing them to lose electrons.
Properties of neutrons in ionising radiation
- not directly ionising.
- high penetrative power due to them having no charge and not interacting strongly with matter.
- so can travel through humans and buildings for long distances before being stopped.
Penetrative and ionising power of alpha particles
Emailed at high speeds. Due to this and their high relative mass, they transfer alot of energy and are good at ionising, however each time ionise an atom they lose energy. Lose energy quickly and have a short penetrative distance because produce many atoms in a short distance
How far do alpha particles travel?
- travel a few centimeters in air
- very ionising
- can be stopped by a sheet of paper
How do beta and alpha particles compare?
Beta particles are much less ionising than alpha so can penetrative much further into the matter than alpha particles can .
How penetrative are beta particles ?
- travel a few metres in air
- moderately ionising
- can be stopped by 3mm thick aluminium
How do gamma rays compare with beta particles ?
Gamma rays about 10 times less ionising than beta and can penetrate matter easily.
