A fair cop! Accurate breath analysis and speed detection
Glossary
anode and cathode. The two electrodes in an electrochemical cell. The anode is the source of electrons, which flow to the cathode. The flow of electrons generates an electrical current. For more information see What is a battery? (Glenn Research Center, NASA, USA)
electrolyte. A substance that produces ions (particles with an electric charge) when dissolved in water. The resulting solution (which can also be referred to as an electrolyte) conducts electricity.
electromagnetic radiation. Electromagnetic radiation is simply energy which travels through space at about 300,000 kilometres per second – the speed of light. We imagine radiation moving like a wave. The distance between two adjacent wave crests is called a wavelength. The shorter the wavelength, the more energetic the radiation is said to be. Also, the shorter the wavelength, the greater the frequency of the radiation. Other than wavelength, frequency and energy there is no difference between a radio wave, an X-ray and the colour green. They all possess the same physical nature. For more information see Back to Basics: Electromagnetic radiation (Australian Academy of Science) and Electromagnetic Spectrum (NASA Goddard Space Flight Center, USA).
electron. A negatively charged particle that is a constituent of an atom. Electrons can move from atom to atom. When they do, they produce an electric current.
frequency. A measure of how frequently an electromagnetic wave goes up and down (oscillates) or the number of waves passing by in a second. A hertz is a unit of frequency – 1 oscillation per second; a kilohertz (kHz) is 1000 hertz – 1000 oscillations per second; a megahertz is 1 million hertz – 1 million oscillations per second. For more information see Sound properties and their perception – pitch and frequency (The Physics Classroom, USA).
fuel cell. A device that converts energy from chemical reactions directly into electrical energy. The simplest fuel cell 'burns' hydrogen in a flameless chemical reaction to produce electricity. In order to 'burn' the hydrogen a fuel cell needs a source of oxygen and this is usually obtained from air. The only by-product from this type of fuel cell is water.
For more information about fuel cells see Fuelling the 21st century (Nova: Science in the news, Australian Academy of Science).
infrared. The part of the electromagnetic spectrum between visible light and microwaves. The wavelength of infrared light is between 0. 7 micrometres (0.0007 millimetres) and 1 millimetre. These wavelengths are longer than those of visible light, but shorter than those of microwaves. (The prefix 'infra' means 'below; infrared refers to radiation below the frequency of red light.)
legal limit of 0.05. The legal limit of 0.05 refers to the blood alcohol concentration (BAC) and is measured in grams of ethanol per 100 millilitres of blood. For example, men and women with a BAC of 0.05 grams per 100 millilitres have 0.05 grams of alcohol in their body for every 100 millilitres of their blood. The legal limit is lower for certain road user groups (eg, those who hold learner or provisional licences). Depending on the state or territory, this lower limit is either zero or 0.02.
national measurement system. Australia's national measurement system is coordinated by The National Measurement Institute. The NMI commenced on 1 July 2004 and is responsible for establishing and maintaining Australia's units and standards of measurement. NMI has been formed from the National Measurement Laboratory (CSIRO) the National Standards Commission and the Australian Government Analytical Laboratories.
photon. A photon is the smallest unit of light energy.
radar. The use of reflected radio waves to determine the location of an object and its speed if it is moving. It is an acronym derived from radio detecting and ranging. For more information see How radar works (How Stuff Works, USA).
radio waves. Low frequency electromagnetic radiation. Radio waves have wavelengths ranging from less than a centimetre to as long as 100 kilometres. The hertz (Hz) is the unit of frequency and means one complete oscillation per second. Many frequencies are much higher than this so other units are used (eg, 1 megahertz (1MHz) = 1,000,000Hz).
We divide the radio wave part of the electromagnetic spectrum into bands that are allocated to different uses. These include AM radio (amplitude modulation), FM radio (frequency modulation) and CB radio (citizens' band), television, aircraft communications, satellites, mobile phones and pagers. Within each band, no two transmissions can use the same part of the spectrum – or frequency – at the same time. For this reason, each band within the radio wave spectrum, itself a part of the broader electromagnetic spectrum, must be managed carefully to ensure the best use of this limited resource.
The frequency of radio waves used in magnetic resonance imaging range from 1-100 megahertz, depending on the strength of the magnetic field in the scanner. This is close to the range of frequencies used for FM radio (88-108 megahertz). For more information see How the radio spectrum works (How Stuff Works, USA).
Page updated March 2005.