| A | B |
|---|
| Alpha radiation | can be stopped by paper |
| Beta radiation | can be stopped by aluminium |
| Gamma radiation | can be stopped by thick lead |
| The energy transferred by a wave depends on the | wavelength |
| Half-life is | the time it takes for the number of radioactive nuclei to halve |
| Radio waves have wavelengths of more than | 1000 m |
| Gamma rays have a wavelength of less than | a millionth of a millionth of a metre |
| Frequency is | the number of waves passing in a second |
| Wave speed = | frequency x wavelength |
| X-rays | provide a picture of the body |
| Gamma rays | can be used to sterilise surgical instruments |
| Ultraviolet | can be used for security marking |
| Visible light | can be used to see |
| Infra-red | can be used for cooking and in optical fibres |
| Microwaves | can be used for heating food and communication |
| Radiowaves | can be used for communication |
| An analogue signal | is any number |
| A digital signal | is either on or off |
