Dr Pusey

What do you think an atom is? Can you draw what it looks like?

TYPES OF RADIATION

• In a radioisotope (an isotope that decays) the nucleus is unstable and may spontaneously emit radiation to become more stable

• There are three different types of radiation:

• Alpha - α

• Beta - β

• Gamma – γ

• This subject is covered in much greater detail in year 11 Physics!

ALPHA RADIATION

• Represented by the lowercase Greek letter ‘alpha’ - α

• Consists of 2 protons and 2 neutrons, it is a helium nucleus

• Positively charged (+2)

• Usually emitted by heavier elements such as uranium and radium

• Can be absorbed by a sheet of paper

• Range in air is only a few centimetres

• Emitted at a velocity of 5-7% the speed of light

α

BETA RADIATION

• Represented by the lowercase Greek letter ‘beta’ - β

• Consists of 1 electron

• Negatively charged (-1)

• Can be absorbed by 3.5 cm of lead or a sheet of aluminium

• Range in air is a few metres

• Emitted with a velocity of 30-90% speed of light

β

GAMMA RADIATION

• Gamma radiation = electromagnetic wave (not a particle)

• No charge, it’s a type of energy, not a particle

• Absorbed by several cm of lead

• Range in air is almost unlimited

• Electromagnetic wave, so it travels a the speed of light

γ

HALF-LIFE

• Different radioisotopes decay at different rates

• Radioactive decay is a spontaneous process that can’t be controlled

• Each radioisotope has its own characteristic decay rate (called half-life)

• The decay rate is unaffected by physical and chemical conditions (e.g. pressure, temperature)

• Half-life (𝑡1/2) = the time it takes for half the atoms in a sample to decay