Download
1 / 34
350 likes | 358 Views
What do you think of radiation?. What is ‘radiation’?. The term radiation (also known as nuclear radiation ) refers to the p articles or waves emitted by radioactive substances. electron. Nuclear radiation comes from the nucleus of a radioactive atom.
E N D
What is ‘radiation’? The term radiation (also known as nuclearradiation) refers to the particles or waves emitted by radioactive substances. electron Nuclear radiation comes from the nucleus of a radioactive atom. An atom has electrons orbiting the outside and a central nucleus, which is made up of protons and neutrons. proton neutron In a radioactive atom, the nucleus is unstable and so it emits particles or waves to form a more stable atom. This process is called radioactivity or radioactive decay. It is a natural and completely spontaneous process.
How can radiation be detected? Radiation is all around us – naturally occurring, and man-made sources, but it is invisible, so how do we actually know it’s there? The effects of radiation can be seen and so it can detected using instruments such as a Geiger-Müller tube. This is a device that can detect and measure radiation. Radioactivity can also be detected by the presence of photographic film, which darkens when struck by radiation. This effect led to the initial discovery of radioactivity more than one hundred years ago.
What is alpha (α) radiation? 2 neutrons, 2 protons Description Note:– An alpha particle is the same as a helium nucleus +2 Electric charge 4 Relative atomic mass Stopped by paper or a few centimetres of air Penetrating power Strongly ionizing Ionizing effect Effect of magnetic/ electric field Weakly deflected
What is beta (β) radiation? High energy electron Description -1 Electric charge 1/1860 Relative atomic mass Stopped by a few millimetres of aluminium Penetrating power Weakly ionizing Ionizing effect Effect of magnetic/ electric field Strongly deflected
Gamma () radiation High energy electromagnetic radiation Description 0 Electric charge 0 Relative atomic mass Stopped by several centimetres of lead or several metres of concrete Penetrating power Very weakly ionizing Ionizing effect Effect of magnetic/ electric field Not deflected
How can radiation detect a fire? Smoke alarms contain a weak source of alpha radiation. The alpha particles ionize the air. If there is smoke present, it interacts with the ions produced by the alpha particles and ionization is reduced. smoke particle α This means that less current is flowing through the air, which causes the alarm to sound. α
How can radiation detect cracks? Gamma rays can also be used to detect cracks after an object has been welded. Gamma rays are like X-rays. welded metal pipe welding flaws If a gamma source is placed on one side of the welded metal, and a photographic film on the other side, any flaws will show up on the film like an X-ray. photographic film
How is radiation used for sterilization? Gamma rays are used to kill bacteria, mould and insects in food. This can be done even after the food has been packaged. It can affect the taste, but supermarkets like it because it lengthens the shelf life. Gamma rays are also used to kill bacteria on medical equipment. It is particularly useful with plastic equipment that would be damaged by heat sterilization.
Radiation safety The three types of radiation differ in their effects and physical nature. All radioactive sources must be handled safely. The hazard symbol for radiation is shown below: As well as the normal laboratory safety rules you follow, are there any extra rules concerning radioactivity?
How are radioactive sources used safely? Radioactive materials could be very dangerous to handle if no safety precautions were taken. This is because people and their clothing could become contaminated. The safety precautions are: • keep exposure times as short as possible • monitor exposure with a film dose badge • label radioactive sources clearly • store radioactive sources in shielded containers • wear protective clothing • use tongs or a robotic arm to handle radioactive materials.
Background radiation Background radiationis the radiation all around us. Most of the radioactivity you are exposed to is from natural sources. How many different sources of background radiation can you think of?
Glossary • alpha radiation –Positively charged particles made up of two protons and two neutrons. • background radiation –Constant low-level radiation from food and environmental sources. • beta radiation – High-energy electronsemitted by some radioactive materials. • gamma radiation – Short-wavelength electromagnetic radiation emitted during radioactive decay. • Geiger-Müller tube –A device used to detect and measure radiation from radioactive materials. • ionizing radiation – High-energy radiation capable of ionizing substances through which it passes. • radioactivity –The spontaneous emission of radiation from the nucleus of an unstable atom.
