Radiation

Question 1

What are the factors that affect temperature?

Answer 1

1. A body at a constant temp absorbs the same amount of radiation as it emits.
2. An object will increase its temperature if it absorbs more radiation than it emits.
3. An object will decrease its temperature if it emits more radiation than it absorbs.

Question 2

What does the temp on earth depend on?

Answer 2

How much radiation is absorbed and how much is emitted.

Question 3

What do energy levels in an atom depend on?

Answer 3

The electrons can move between the shells or leave the atom completely.

Question 4

When is electromagnetic radiation emitted?

Answer 4

When electrons fall down from higher to a lower energy level.

Question 5

Where is energy also emitted from?

Answer 5

Energy is also emitted from the nuclei of unstable atoms. When energy changes occur in the nucleus, gamma rays are emitted.

Question 6

What radiations are emitted from an unstable nuclei?

Answer 6

Alpha, Beta, Gamma and Neutron radiation.

Question 7

When do elements undergo radioactive decay?

Answer 7

Some elements are radioactive because their nuclei is unstable so they will undergo radioactive decay and change into other elements.

Question 8

What is an alpha particle?

Answer 8

Helium nucleus
- 2 Protons + 2 Neutrons
- Has a charge of +2 and is the heaviest.

Question 9

What is a beta particle?

Answer 9

An electron
- Charge of -1

Question 10

What is a positron?

Answer 10

An anti-electron
- Has a charge of +1

Question 11

What is a gamma ray?

Answer 11

High energy electromagnetic radiation that has no charge and no mass.

Question 12

What particles can ionise?

Answer 12

• Alpha, Beta and Gamma.
• Can collide with atoms and ionise them causing them to loose electrons.

Question 13

What are the properties of neutrons?

Answer 13

• not directly ionising
• have a very high penetrating power due to them having no charge and not interacting strongly with matter.
• can travel through humans and buildings for long distances before being stopped.

Question 14

What are the properties of Alpha?

Answer 14

• travel around 5cm in air.
• very ionising.
• can be stopped by a sheet of paper.

Question 15

What are the properties of Beta?

Answer 15

• travel a few meters in air.
• moderately ionising.
• can be stopped by aluminium 3mm thick.

Question 16

What are the properties of gamma?

Answer 16

• will travel a few kilometres in air.
• weakly ionising.
• need thick lead to stop them.

Question 17

Can you name some examples of background radiation?

Answer 17

• Radon gas
• Food and drink
• Cosmic rays (from space)
• Nuclear power
• Medical
• Ground and buildings
• Other

Question 18

How do you measure radioactivity?

Answer 18

• The Geiger-Muller tube
  = its is connected to a counter or a ratemeter which shows the amount of radiation that has been detected.

Question 19

How do we detect radiation?

Answer 19

Photographic film
= Radiation causes the darkening of the film and this caused the development of workers wearing a film badge to detect how expose they are.
- A Dosimeter is a film badge.

Question 20

What is Beta minus decay?

Answer 20

• A neutron decays to become a proton and an electron.
• The proton stays in the nucleus but the electron, which is the beta minus particle, is emitted from the nucleus at high speed as a fast moving electron.
• The mass number doesn’t change but the proton number increases by 1.

n——–>p+e-

Question 21

What is Beta plus decay?

Answer 21

• A proton decays to become a neutron and a positron. The neutron stays in the nucleus.
• The positron, which is the beta plus particle, is emitted from the nucleus at a very high speed, carrying away a positive charge and a small amount of the nuclear mass.
• p ——–> n + e+
• The mass number doesn’t not change but the proton number decreases by 1.

Question 22

What are the changes to the nucleus due to decay?

Answer 22

alpha a=
- nuclear mass reduced by 4 ( -4 )
- positive charge reduced by 2 ( -2 )

beta minus=
- no change to mass
- positive charge increased by 1 ( +1 )

beta plus=
- no change to mass
- positive charge reduced by 1 ( -1 )

gamma=
- no effect to either mass or charge.

neutron=
- mass is reduced by 1 ( -1 )
- no change to nuclear charge.

Question 23

What is radioactivity measured in?

Answer 23

Becquerel ( Bq )

Question 24

What is a half-life?

Answer 24

The half-life of a radioactive isotope is the time it takes for half of the unstable atoms to decay

Question 25

How do you work out half-life?

Answer 25

- Half the activity - 1 half-life = x1/2 - 2 half-lives = x 1/2 x 1/2 - 3 half-lives = x 1/2 x 1/2 x 1/2 which is x1/6

Question 26

What are the uses of Gamma rays?

Answer 26

- kills cancer cells - sterilise surgical instruments - diagnose cancer = a radioactive isotope tracer solution emits gamma rays. - preserve food

Question 27

What are the uses of alpha particles?

Answer 27

Smoke alarms

Question 28

Why are beta particles used to control the thickness of paper?

Answer 28

Alpha would not go through the paper. - Gamma would pass through the paper too easily and the amount getting through would hardly change the thickness of the paper.

Question 29

What are the dangers of radiation?

Answer 29

- Energy transferred by ionising radiation removes electrons from atoms to form ions. - Ions are reactive and can cause mutations to the DNA in cells - Damaged DNA can lead to cancer.

Question 30

What are the precautions and safety for being around radiation?

Answer 30

1) limiting the time of exposure 2) wearing protective clothing= wearing a lead apron will absorb much of the ionising radiation. 3) Increasing the distance between person and radioactive source= the further the person, the less damage it will do. -move the radioactive source with tongs. - The greater the half-life of a resource, the longer it will remain dangerous.

Question 31

What is irradiation?

Answer 31

- Ionising radiation from an external radioactive source travelling to the body - it is NOT breathed in, drank or eaten. - this could be from harmful gamma rays, beta particles or X-rays.

Question 32

What is contamination?

Answer 32

- Radioactive materials come into contact with a person's hair, skin or clothing. ( this is external contamination ) - Internal contamination is when a radioactive source is eaten or drunk.

Question 33

What are medical tracers?

Answer 33

Substances that are used in biological processes in the body and contain a radioisotope. - a patient can eat or drink this substance or it can be injected into the body. - ionising radiation is emitted by the tracer and can be detected and the processes are monitored.

Question 34

What are PET scanners?

Answer 34

Produce 3D colour images of the internal workings of the patient. 1) tracer is a radioactive material that decays quickly by emitting positrons. 2) when the positrons come into contact with electrons in the body, the two particles annihilate each other, resulting in the formation of gamma-rays. 3) gamma rays are detected by the PET scanner and the computer processes it, an image is then shown. 4) As the tracers decay quickly, they need to be produced close to where they are used.

Question 35

How are internal tumours treated?

Answer 35

1) Injecting the radioisotope into the patient. 2) the patient eating or drinking something which contains the radioisotope in solid or liquid form.

Question 36

How are external tumours treated?

Answer 36

1) gamma rays are fired, from different positions, towards the cancer. 2) each ray is not energetic enough to kill the tumour, but damages it. 3)by moving the ray, the amount of ionising radiation received by the surrounding tissue is reduced.