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