Radioactivity Flashcards

Question

are neutrons ionising (2)

Answer 1

Neutrons are not DIRECTLY ionising as they don’t have a charge but they are indirectly ionising as Neutrons can cause other other atoms to become radioactive ⟶ neutrons are the only radiation that can cause other atoms to become radioactive

Answer 2

A geiger counter/ geiger-muller tube - instruments that detect radiation

Answer 3

For alpha particles: A= 4 Z = 2

Answer 4

For B- particles: A= 0 Z= -1

Answer 5

For neutrons: A = 1 Z = 0

Answer 6

In X-rays, the radiographic film starts off as white but turns black when it absorbs radiation So, bones appear white as they do not let any radiation through however soft tissue lets SOME through, so it appears as different opacities of white/grey

Answer 7

In order to be aware of their radiation exposure, radiographers wear a photographic film badge ⟶ with more and more radiation exposure to the radiographer, the badge turns darker and darker

Answer 8

The geiger counter set up: A glass tube with an electrically conducting layer on the inner layer of the glass 2. One circular surface of the cylindrical tube has a thin mica window 3. Inside the tube, there is a specific mixture of gas at very low pressure 4. In the middle of the tube, there is an electrode (this is insulated from the conducting surface)

Answer 9

This electrode is connected via a high value resistor to a high voltage supply of 300-500V

Answer 10

How the Geiger-Muller tube works: When ionising radiation enters the tube, it ionises the low pressure gas atoms into ions The newly formed ions can now conduct electricity from the electrode to the conducting layer around the tube This conduction in the conduction layer is detected by an electrical circuit which is normally linked to a counting circuit The counting circuit counts amount of/how many gamma rays/ionising particles have entered the GM tube

Answer 11

Rate meters have a loudspeaker ⟶ the level of radioactivity is shown by the number of clicks produced

Answer 12

Background radiation = low level ionising radiation that is produced all the time It has some natural and artificial sources

Answer 13

Sources: Mnemonic BACKGROUND (no AKU) Buildings A Cosmic Microwave Background Radiation (CMBR) K Ground Radon gas Other (medical etc) U Nuclear power Drinks and food

Answer 14

Some background radiation comes from the Earth’s crust The Earth’s crust has contained many radioactive isotopes Some isotopes are still present today and decay at random releasing radiation Some radioactive products are gases so these will be released out of the crust

Answer 15

Sometimes when radioactive decay happens the product will be another radioactive isotope

Answer 16

Uranium is a radioactive element that decays very slowly

Answer 17

The level of radioactivity from the crust varies location to location as different locations have different levels of radioactive material in the crust

Answer 18

Really big, violent nuclear reactions happening in stars in space and in big stars called supernovae produce cosmic rays The Sun itself releases cosmic rays, but lower energy ones Earth’s atmosphere provides a lot of protection against cosmic rays however do still reach the Earth’s surface

Answer 19

Cosmic rays = very high energy particles which hit the Earth

Answer 20

Humans and other living things also emit some radiation, as the atoms that form our bodies were actually made in stars once upon a time - so we will have a very small amount of radioactive carbon (C-14) Humans eat C-14 and other radioactive isotopes when eating other living organisms, as they are present in all living things

Answer 21

We use radioactive material in nuclear power stations to generate electricity These nuclear power stations leak some radioactive material into the environment

Answer 22

There have also been big leaks, like Chernobyl (Ukraine) and Fukushima (tsunami and earthquake in Japan) This huge leak of radioactive material in the surrounding land water and air made it unsafe for humans to live there

Answer 23

Testing for nuclear weapons has increased the amount of radioactive isotopes on the Earth

Answer 24

Radioactive traces are used in medical scanning, and also as a form of treating cancer BUT medical stuff doesnt contribute much to the overall background radiation

Answer 25

Radioactive decay is RANDOM - we can’t tell which nuclei are going to decay when With time, the number of disintegrations per second goes down as the more nuclei decay, the less there will be left TO decay

Answer 26

Half-life is a measure of activity Half life = the time taken for half the original mass of radioactive sample to decay

Answer 27

With half-life, we assume that if the amount of the radioactive substance has halved, the activity/decay will half Different radioactive isotopes have different half lives

Answer 28

To measure the half-life of a radioisotope, you would measure the activity of the sample at regular times using a GM tube linked to a rate meter VERY IMPORTANT!!!! - before taking any measurements, it is ESSENTIAL to measure the background radiation levels The background radiation levels are subtracted from the measurements

Answer 29

If a radioactive has a short half-life, it means the radioactive decay finishes quite quickly Radioisotopes with short half-lives are very useful in medical fields

Answer 30

example, carbon radioactiviy is 240 baquerels, and it goes down to 30, in 2 hours, so 240 is halfed 3 times, so 240 x 0.5^3 is 30, so in 120 mins, every 40 mins it halfed bc 120/3 is 40

Answer 31

Radioactive tracers = chemical compound that emits gamma radiation This will be either swallowed orally or given to the patient as an injection Once inside, it can be traced using a gamma ray camera

Answer 32

Iodine-123 is used to visualise the thyroid clearly - it has a short half life so that the radiation levels drop to a very low level quite quickly Low doses radiation may have no lasting effect

Answer 33

Higher doses of radiation ⟶ this can stop our cells from working properly or the radiation can damage the DNA in cells ⟶ leads to abnormal growth and cancer Very high doses will kill living cells

Answer 34

To minimise the damage, chemicals are used to target the location of the cancer first ⟶ these may emit alpha or beta radiation (short range so will only affect the tissues nearby)

Answer 35

Gamma radiation is used for sterilisation ⟶ killing bacteria and viruses - it is used to sterilise surgical equipment Food CAN be sterilised with radiation, however this is not done much as people don’t want irradiation of the food Gamma ray cameras are like X-ray cameras ⟶ it is used in factories to identify faults in casting (making things out of metal) or welding (joining metals together)

Answer 36

Why gamma over X-ray ⟶ it can be cheaper overall as gamma sources can be small so don’t require a power source or large equipment

Answer 37

Radioactive isotopes are used to gauge (to measure) how much material there is in a storage container Coal absorbs a large amount of radiation ⟶ reading on lower detectors will be small, and upper detectors, where that part of the container is empty, will have high readings Radioisotopes are used to check the flow of liquids in industrial processes ⟶ very tiny amount of radiation can easily be detected ⟶ used to monitor for leaks in places with complex piping systems or to measure the rate of spread of sewage

Answer 38

Radiocarbon dating uses C14 levels How C14 becomes a part of living organisms: 1. When cosmic rays hit some gases in the atmosphere, it can cause the nuclei to break apart - when they break apart they fly off at high speed, and can hit into other atoms and cause nuclear transformations 2. This is seen with Nitrogen (78% of our atmosphere) 14/7N + 1/0n ⟶ 14/6C + 1/1 p n = neutron p=proton 3. This C-14 that is produced reacts with the oxygen in the air to form CO2 ⟶ so now we have C-14 in the air 4. This CO2 is absorbed and incorporated into plants via photosynthesis 5. C-14 moves through the food chain as the plant etc gets eaten Although these C-14 atoms decay, they are continuously replaced by new ones in LIVING plants and animals When an organism dies, this replacement of C-14 stops When it dies, the C-14 will be decaying, so the proportion of C14 compared to C-12 decreases, using half life equations we can calculate the period in which the animal was living

Answer 39

Limitations to radiocarbon dating: 1. It assumes that the level of cosmic radiation reaching Earth is constant (which isn’t necessarily true)

Answer 40

With a very small amount of ionising radiation, (background radiation), the cells repair themselves - they often die with too much exposure to ionising radiation

Answer 41

Alpha radiation - low risk, as even though it is the most ionising, its range is so short and it is not penetrating at all - it cannot get through our skin However, alpha emitters can be breathed in or eaten in food

Answer 42

Radon gas is an alpha emitter so is an alpha emitter and smokers are at huge risk with this

Answer 43

Beta and gamma radiation provide a serious health risk when outside of the body ⟶ both can penetrate our skin and flesh and cause cell damage by ionisation With regards to inside the body, gamma and beta provide less risk compared to alpha With all the types, the longer/greater the exposure to radiation, the greater the cell damage.

Answer 44

Another type of badge (other than the film one) is a thermoluminescence badge This badge means that exposed material will give out light when it is warmed ⟶ radiation releases energy to make heat, so the greater the radiation, the more light it gives out

Answer 45

Being safe with radioactive material: storing radioactive materials in lead-lined containers (this will block even gamma rays, the most penetrating) The containers will be laeled as radiation hazard

Answer 46

In power plants, the workers and handlers are protected by lead shields, concrete and thick glass viewing panels Wate materials and fuel rods from nuclear reactors are stored under water until the neutron radiation levels drop to a safe level