Low level radiation that is around us all the time 1) What is background radiation Answer Low level radiation that is around us all the time

2) What is the name of the radioactive gas that is found around us? Radon

3) Where are the three places naturally occurring radiation come from (3). Answer i) unstable isotopes from around us, air food, rocks ii) Radiation from the sun (cosmic back ground radiation) iii) Radiation from human activity

4) Where does radiation from human activity come from. Ans: nuclear explosions dumped nuclear waste. .

5) What type of ionising radiation does Radon gas emit Ans: Gamma. .

6) Define half life Ans: The time it takes for HALF the NUMBER of radioactive particles to decay is called the HALF LIFE. .

7) Work out the half life from this graph Ans: 2 days .

8) The activity of a radioisotope is 800 bq 8) The activity of a radioisotope is 800 bq. 30 minutes later it has fallen to 100 Bq. Find the half life of the sample. Ans: 800--400-- 200----100 How many half lives has it taken to reach 30? 3. So if 30 minutes represents 3 half lives, so how long is one half life. 10 minutes .

9) A radioactive isotope has a half life of 15 minutes 9) A radioactive isotope has a half life of 15 minutes. It has an initial count rate of 6000 Bq. What will the count rate be after 1 hr and 15 min? Ans: 6000--3000-- 1500----750-- 325----163 15 30 45 60 1hr 15 min Answer = 163 .

10) Name one application of alpha radiation Ans: Smoke alarms

11) How alpha radiation is used in fire alarms (3) Ans: Alpha radiation source placed between two electrodes inside smoke alarm. Source causes ionisation which results in a current to flow. In the event of a fire, smoke will get in between the electrode and absorb the radiation. This will stop the current to flow and alarm will sound

12) Name some application of gamma radiation Ans: Preserving food by killing microbes Sterilisation of medical equipment Treating cancer Used in industry to detect leaks in underground pipes .

13) Name a use of beta ionisation Ans: Medical tracers Controlling the thickness of paper.

14) Explain how beta and gamma radiation is used as medical tracers. Ans: Radiation is either swallowed or injected. Computer traces the injected isotope around the body to create an image. Can be used to detect cancer.

15) Why do medical tracers need to be beta or gamma and not alpha? Ans: So radiation passes out of the body minimising exposure. Alpha radiation will not be able to pass out.

16) Why do medical tracers need to have a very short half life. Ans: The radioactive isotopes will disappear quickly minimising the overall exposure anyone close to contact with it

17) Explain how beta radiation is used to control the thickness of paper. Ans: From one side direct radiation through paper and have detector on the other side attached to a control unit. When the detected radiation changes this means the paper coming out is too thick or thin. The control unit adjust the rollers to give the correct thickness.

18) Why is alpha and gamma radiation not used to control the thickness of paper. Ans: Alpha-not penetrating enough-stopped by paper. Gamma-to penetrating, goes straight through and sound alrm

19) Describe some disadvantages of nuclear radiation (2). Ans: Not easy to dispose of. Danger it could leak out and pollute rivers, oceans and land. Overall cost of nuclear power is high-high initial setup costs and decontamination costs/

20) Describe some advantages of nuclear radiation (6). Ans: Reduces the need for fossil fuels. Does not release CO2, that means does not contribute to global warming. Does not release SO2, so does not cause acid rain Huge amounts of energy created from very little fuel. It is cheap and readily available.

21) Describe the factors that need to be considered when radioactive waste is disposed under ground (4). Ans: the long time taken for decay (of long-lived radionuclides) • water causing corrosion / leaks • transportation of radioactive material • need for geologically stable rock formation • public perception of waste • security from terrorist activity

22) Describe why back ground radiation can be detected all the time and not just detected during radioactive experiments. Ans: It is all around us. It is given off by radon gas, food, cosmic rays, rocks and medical x-rays.

23) What is the largest contributor of background radiation. Ans: Radon gas

24) Explain why gamma radiation is sprayed over food in super markets. Ans: • (gamma) will penetrate packaging (1) • (to) destroy microorganisms (1) • (by) ionisation (1)

25. Describe how radioactive waste is disposed of. Lead concrete barriers to prevent leakage.

The diagram shows how rollers can change the thickness of paper in a factory. A thickness gauge controls the rollers. The thickness gauge contains a radioactive source and a detector. If the paper is too thick, the reading on the detector goes down. This causes the rollers to be pushed closer together. The radioactive source used must be chosen carefully to be effective and used in a way that is not a hazard to workers. Discuss the factors to consider when choosing and using this radioactive-(make reference to half life)

Markscheme Appropriate type of radiation is chosen - some passes through - – β and γ not α - significant change with thickness - - β Half-life - reference to half-life - not too long - too much material needed for activity - not too short – expense of replacing regularly - disposal problems Safety issues - shielding • type of radiation, linked to appropriate material and thickness - security • storage of spares in use - safety procedures / precautions in use