Radiation

Question 1

What is carbon dating

Answer 1

Uses isotope carbon 14. It is used to find out how old something is

Question 2

How does carbon dating work

Answer 2

Only works for materials that were once living. Living organisms take in carbon 14 but when they die the replacement process stops. Carbon 14 has a half life of 5600 years, so we can work out how long ago something e.g a tree died by comparing the amount of carbon 14 left in it to with how much would be in a similar living organism.

Question 3

What are possible problems with carbon dating

Answer 3

Assumes the level of cosmic radiation reaching the earth is constant . Also inorganic living matter e.g rocks and minerals does not absorb carbon 14

Question 4

What is carbon 14

Answer 4

Made when high energy neutrons collide with nitrogen atoms . The high energy neutrons are formed when cosmic rays cause atoms in the atmosphere to break up

Question 5

How do we date radioactive rocks

Answer 5

Inorganic matter and non living matter does not absorb carbon 14 we need to use other elements to date them. When a radioactive isotope decays, the original isotope is called the parent nuclei. If the products of decay also decay we get a decay series , at the end of this we have a stable isotope. In a rock the proportion of parent to stable daughter nuclide gives a measure of the age of the Rock

Question 6

How can we product radiographer a

Answer 6

Monitor their exposure to radiation and make sure they handle it from a safe distance

Question 7

How can we store nuclear waste

Answer 7

In sealed lead containers capable of holding radiation for enormously long periods of time

Question 8

What is the nucleus of an atom

Answer 8

Contains protons and neutrons and make up the mass of the atom

Question 9

What is the atomic number

Answer 9

Total number of protons , elements are ordered in this order

Question 10

What is the mass number

Answer 10

Protons + neutrons

Question 11

What are isotopes

Answer 11

Many elements have a few different isotopes. Isotopes are atoms with the same number of protons (atomic number) but a different number of neutrons ( different mass number). Usually each element has only one of two stable isotopes like carbon 12. The other isotopes tend to be radioactive , the nucleus is unstable so it decays and emits radiation

Question 12

How does radioactive decay work

Answer 12

Random. Unaffected by physical conditions .when the nucleus does decay it splits out one or more of three different kinds of radiation - alpha , beta and gamma. In the process the nucleus often changes into s new element

Question 13

What is background radiation

Answer 13

Low level background nuclear radiation around us all the time comes from : substances on earth e.g food air building materials soil rocks
Radiation from space (cosmic rays )that come mostly from the sun
Living things
Radiation due to human activity e.g fallout from nuclear explosions or nuclear waste

Question 14

What is ionisation

Answer 14

Nuclear radiation causes ionisation by bashing into atoms and knocking electrons off them. Atoms are turned into ions. The further the radiation can penetrate before hitting an atom the less damage it will do so a less ionising

Question 15

What are alpha particles

Answer 15

2 protons and 2 neutrons . Big heavy slow moving. Don’t penetrate far into materials but are stopped quickly. Because of their size they are strongly ionising , which means they bash into a lot of atoms and knock electrons off them before they slow down , which creates lots if ions . They’re electrically charged (positive) they can be deflected by electric and magnetic fields. Emitting an alpha particle decreased the atomic number by 2 and the mass number by 4

Question 16

What are beta particles

Answer 16

An electron which had been emitted from the nucleus of an atom where a neutron turns into a proton and an electron . When s beta particle is emitted the number of protons in the nucleus increase by 1 (atomic number ) but the mass number stays the same. The move quite fast and are quite small. Penetrate moderately and are moderately ionising . Because they’re negatively charged they can be deflected by electric and magnetic fields

Question 17

What are gamma rays

Answer 17

Short wavelength electromagnetic waves. They’re just energy. Can penetrate a long way into materials without being stopped but this means they are weakly ionising as they tend to pass through atoms instead of colliding but when they hit something they do damage. They have no charge and are not deflected by electric or magnetic fields . Gamma emission happens after beta or alpha decay. Has no effect on mass or atomic number of atom it is just the nucleus emitting excess energy in the form of a gamma ray

Question 18

What are the radiation blocked by

Answer 18

• alpha particles blocked by paper skin , few cm of air
• beta particles stopped by thin metal
• gamma rays blocked by thick lead or very thick concrete

Question 19

How can gamma rays be used to treat cancer

Answer 19

Gamma source is moved around the body of the patient so that the rays go through the cancer cells but go through a different part of the healthy tissue each time to keep the damage of the healthy cells down to a minimum

Question 20

How is radiation used in sterilisation

Answer 20

Because radioactive radiation destroys cells it can be used to destroy bacteria . Food or medical instruments do not need to be taken out of their packaging - the radiatiOn will pass through it and destroy the harmful organisms inside.

Question 21

How can radiation be used in thickness and measurement control

Answer 21

Radioactive source emits beta particles which can pass through the metal , the thicker the metal the more beta particles there are absorbed so the lower the reading on the detector . For thin sheets more beta particles get through so the reading on the detector is higher. By first using carefully measured thickness of metal the correct reading on the meter is recorded and marked on the scale if the reading is above the scale , the metal is too thin if it is below the scale it is too thick. The meter is usually coupled to the machine which controls the rollers and as its readings change it adjusts the rollers so that the sheet of metal is produced at the correct thickness

Question 22

How can we measure radiation

Answer 22

Photographic film or Geiger muller detector

Question 23

How are radioactive tracers used

Answer 23

Radioactive fertilisers can be fed to plants and then traced through the plant using a Geiger muller counter . This is used to delevop better fertilisers and incesticides. Similarly in hospitals and isotope with a short half life is injected into a patients body . A gieger muller counter is used to trace the movement of the chemical through the patients body , to check that certain glands are functioning properly. Tumours can be located beachside they take up more radioactive isotope than other parts of the busy

Question 24

How can means from a pipeline be detected

Answer 24

Inject a radioactive isotope into the pipeline so leaks can be detected

Question 25

How do you use gamma radiation to check welds

Answer 25

Gamma source placed on one side of the welded metal and photographic film on the other side , weak points will show up when the film is developed

Question 26

How can beta be used in factory’s

Answer 26

When the box passes through beta particles are blocked the machine counts the number of beta particles blocked if a box is not full the detector eoll drop

Question 27

What is half life

Answer 27

Measured in becquerel 1 bq- 1 decay per second

1. Half life is the average time for the activity of a radioactive sample to fall to half its original value

Question 28

What is beta decay

Answer 28

Neutron spontaneously changes into a proton and electron . The proton stays in the nucleus ,the electron comes out as a beta particle

Question 29

What are the hazards of ionising radiation

Answer 29

Can damage the Molecules that make up the cells of moving tissue . Usually no permnent damage is done . However if cells suffer repeated damage because of ionising radiation the cell might be killed . Alternatively the cells may behave in an unexpected manner , we call this effect cell mutation

Question 30

When do alpha particles have the most risk

Answer 30

As they re the most ionising but have little penetrating power they only present risk if they are taken inside the body , meaning that the radiation will be very close to different kinds of cells that may be damaged if the exposure is prolonged

Question 31

How can alpha emitters enter the body

Answer 31

Can be breathed in or taken in through eating food . Radon gas , present in cigarettes is a decay product of radium an alpha emitter it therefore presents a risk to health by smoking you increase your risk as radon is drawn into your lungs

Question 32

How are beta and gamma risky

Answer 32

prove a serious health risk outside the body as both can penetrate skin and cause cell damage outside the body . Gamma is the most penetrating and the damage caused by gamma will depend on how much of their energy is absorbed by ionising atoms in their path. Beta and Gamma absorbed by the body present less risk than alpha because of their lower ionising ability

Question 33

How can you increase the risk of serious cell damage

Answer 33

The longer the period of exposure to radiation

Question 34

How is the exposure limited

Answer 34

Workers in nuclear industry wear badges that indicate their level of exposure . Samples of radioactive isotopes used in school are very small and are stored in led containers and are labelled as radiation hazards and mocked in a metal cabinet. They are handles with tongs to keep them as far away from the body as possible

Question 35

How are energetic sources handled in the nuclear industry

Answer 35

Handled by operators shielded in lead concrete and thick glass viewing panels

Question 36

Why is it important to dispose of radioactive waste safly

Answer 36

It’s dangerous as it is harmful as it contains radioactivity which causes cell damage and mutation it also can Have very long half half lives and remain active for enormously long periods of time and future generations need to know where the waste is so they don’t build settlements on top of it