KS4 Radioactivity

AlphaBetaGamma Penetrating power Range of radiation leastmediummost shortestmediumlongest

Thin tissue paper Thin aluminium stops BETA Thick lead reduces GAMMA Skin or paper stops ALPHA The penetration power of the three types of radiation.   

The effects of a field on radiation Gamma radiation has no mass or charge so it is not deflected. Beta radiation has a –1 charge and a small mass so is strongly deflected Alpha radiation has a +2 charge but a RAM of 4 so is only weakly deflected. The effect of a magnetic or electric field on radiation depends upon the nature of the radiation.

AlphaBetaGamma Penetrating power Range of radiation Most dangerous outside of body Most dangerous inside of body Affected by a magnetic field leastmediummost shortestmediumlongest leastmediummost mediumleast yes no

Alpha radiation -  Helium nuclei Description: 2 neutrons, 2 protons (helium nuclei) Electric Charge: +2 Relative Atomic Mass: 4 Penetration power: Stopped by paper or a few cm of air Ionisation effect: Strongly ionising Effects of Magnetic/Electric Field: Weakly deflected

Beta radiation -  high energy electron Description: High energy electron Electric Charge: Relative Atomic Mass: 1/1860th Penetration power: Stopped by few mm of aluminium Ionisation effect: Weakly ionising Effects of Magnetic/Electric Field: Strongly deflected

Gamma radiation -  Electromagnetic radiation Description: High energy electromagnetic radiation Electric Charge: 0 Relative Atomic Mass: 0 Penetration power: Reduced by several cm’s of lead or several metres of concrete Ionisation effect: Very weakly ionising Effects of Magnetic/Electric Field: NO deflection

Match the radiation Alpha Beta Gamma Helium nuclei High energy electron Electromagnetic radiation Stopped by paper or skin Reduced by lead Stopped by aluminium

Ionising radiation If the exposure is high, it can kill the cell. If the exposure is lower it can cause cancer. The higher the exposure, the higher the risk of cancer. Alpha is the most ionising radiation, gamma is the least. What happens if radiation is incident upon a living cell? Ionising radiation can be used to kill cancer cells. Radiation can ionise cells which causes cellular damage.

Ionisation questions 1.What is ionisation? 2.How is a neutral atom positively ionised? 3.How is a neutral atom negatively ionised? 4.What two effects on living cells can ionisation have? 5.Which type of radiation is the most ionising? 6.Which type of radiation is the least ionising? When a neutral atom loses or gains electrons and hence charge. By losing electrons. By gaining electrons. Kill cells or cause cancer. Alpha radiation. Gamma radiation.

Which type of radiation is….. 1.The most penetrating? 2.The least penetrating? 3.Least dangerous outside the body? 4.Most dangerous inside the body? 5.High energy electrons? 6.Has a negative charge? 7.Is weakly ionising? 8.Has zero charge and zero mass? 9.Only reduced in intensity by lead and concrete? Gamma Alpha Beta Gamma

Uses of radiation

Sterilisation 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 hospital equipment. It is particularly useful with plastic equipment that would be damaged by heat sterilisation. 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 hospital equipment. It is particularly useful with plastic equipment that would be damaged by heat sterilisation. Gamma Source unsterilisedsterilised

Radiotherapy A carefully controlled beam of gamma rays can be used to kill cancer cells. It must be directed carefully to minimise the damage to normal cells. However, some damage is unavoidable and this can make the patient ill. It is therefore a balancing act - getting the dose high enough to kill the cancerous cells, but as low as possible to minimise the harm to the patient. A carefully controlled beam of gamma rays can be used to kill cancer cells. It must be directed carefully to minimise the damage to normal cells. However, some damage is unavoidable and this can make the patient ill. It is therefore a balancing act - getting the dose high enough to kill the cancerous cells, but as low as possible to minimise the harm to the patient.

Leak detection in pipes The radioactive isotope is injected into the pipe. Then the outside of the pipe is checked with a Geiger-Muller detector, to find areas of high radioactivity. These are the points where the pipe is leaking. This is useful for underground pipes that are hard to get near. The radioactive isotope must be a gamma emitter so that it can be detected through the metal and the earth where the pipe leaks. Alpha and beta rays would be blocked by the metal and the earth. The isotope must have a short half life so the material does not become a long term problem. GM tube

Hydraulic ram detector Thickness Control Mill Electronic instructions to adjust rollers. Beta Source A radioactive source is on one side of the material and a detector on the other. If too much radioactivity is getting through, then the material is too thin and the rollers open up a bit to make the material thicker. If not enough radioactivity is detected then the rollers compress to make the material thinner. This method is used in the manufacture of lots of sheet materials: plastics, paper, sheet steel.

Detecting radiation Gieger-Muller Tube Spark counter Photographic film Cloud chamber What are the different methods?

Photographic film 1. What happens to film when radiation is incident upon it? It darkens. 2. Can photographic film tell you the type of radiation incident upon it? No, just the amount of radiation received. 3. What can this be used for? Can be used in radiation badges, that record the exposure of workers to radiation. Different windows detect different types of radiation.

mica window Argon gas Geiger-Muller Tube counter collision & ionisation radiation The detector is a metal tube filled with gas. The tube has a thin wire down the middle and a voltage between the wire and the casing. When the radioactivity enters the tube, it ionises the gas in the tube. This produces a pulse of current which is amplified and passed to a counter. The Argon contains a little bromine to act as a quenching agent and prevent continuous discharge. Good at detecting alpha and beta, not as good at detecting gamma. Argon gas

The Spark Detector The spark detector consists of a metal grid and a metal strip. A high voltage is applied between the grid and the strip. The voltage is increased until electrical arcing (sparking) across the gap just occurs. When ionising radiation is placed close to the detector there is a marked increasing in the amount of sparking. High voltage supply Which type of radiation will be detected the best? Why?

Cloud chamber Cloud chambers show the actual paths of the ionising particles. They rely on ionisation. The cloud chamber is cooled and then is super-saturated with alcohol. If an ion is formed a droplet of condensation appears. Best for alpha radiation as alpha most ionising; then Beta which shows faint traces, but cloud chambers are not as good for gamma as gamma is only weakly ionising. Solid carbon dioxide Radioactive source Cooled alcohol vapour

Which type of radiation is the most penetrating? A.Alpha B.Beta C.Gamma D.X rays

Which type of radiation is the most damaging inside the body? A.Alpha B.Beta C.Gamma D.X rays

Which type of radiation is the most dangerous outside the body? A.Alpha B.Beta C.Gamma D.X rays

Which of the following is not a use of radiation? A.Pre-natal scans B.Radiotherapy C.Smoke detectors D.Detecting leaks