Topic 6-Radioactivity

Question 1

What was Thompson’s model called and what was it?

Answer 1

The plum pudding model. Postively charged material with negative electrons scattered through it.

Question 2

What did Rutherford suggest?

Answer 2

Rutherford suggested that atoms were mostly empty space with most of the mass in a tiny central nucleus with a positive charge and electrons moving around the nucleus.

Question 3

What is ionising radiation?

Answer 3

When an atom gains so much energy one of the electrons jumps to a higher orbit and escapes due to radiation. When an atom gains or loses an electron it is an ion.

Question 4

What is backround radiation?

Answer 4

Radiation that is around us at all times at a safe level(radiation is measured in Benquerels or counts per minute).

Question 5

What are some of the sources of backround radiation?

Answer 5

radon gas 49-rocks that contain uranium

food and drink 10

cosmic rays 10

medical 15

Question 6

What are cosmic rays?

Answer 6

Charged particles from stars.

Question 7

How can radioactivity be measured?

Answer 7

Using photographic film which darkens or with a geiger muller tube and counter. Newer dosmimters change colour without needing to be developed.

Question 8

How do geiger muller tubes work?

Answer 8

Radiation ionises gas inside it and creates a pulse of current.

Question 9

What are alpha particles?

Answer 9

Helium nucleus(2p 2n)-most ionising but least penetrative.

Question 10

What are gamma rays?

Answer 10

EM radiation-energy instead of particles like other two-most penetrative but least ionising.

Question 11

What are beta particles?

Answer 11

High speed, high energy electrons that have been emited from radiation

Question 12

What is a positron emission? b+ decay.

Answer 12

When a proton goes to a neutron and a positron.

Question 13

What is a neutron emission?

Answer 13

This is just when a neutron leaves.

Question 14

Why do atoms decay?

Answer 14

To become more stable.

Question 15

What is b- decay?

Answer 15

A neutron changes into a proton and an electron.

Question 16

What is a half life?

Answer 16

Time it takes for radioactivity to half.

Question 17

How can radiation be used to kill microorganisms?

Answer 17

Food can be irradiated or surgical instruments taht would melt if heated(plastic) can be sterilised.

Question 18

How can radiactive tracers be used for water pipes?

Answer 18

A gamma source can be added to water pipes so when it leaks a geiger muller tube can be used above the ground to detect leaks.

Question 19

How can radiation be used to check for thickness?

Answer 19

Question 20

How can radiation be used in smoke alarms?

Answer 20

Question 21

What are the dangers of radioactivity?

Answer 21

It can cause cancer.

Question 22

What is contamination?

Answer 22

If an object has a radioactive material introduced into it(somethething inside).

Question 23

Whatis irradiation?

Answer 23

Exposing objects to beams of radiation is called irradiation(going through something from outside).

Question 24

How can you diagnose with positrons?

Answer 24

Tracers that emit positrons can be put into the body as when they meet with an electron theyare destroyed and release 2 gamma rays. The detector in a PET scan will see this.

Question 25

How can you diagnose with gamma cameras?

Answer 25

Different organs take up different amounts of molecules and a gamma camera can observe the tracers and make sure the organs are working properly and there are no tumours.

Question 26

Why do radioactive isotopes uses for medical tracers need to have a short half life?

Answer 26

So other parts of body are affected the least so they need to be produced close and recently.

Question 27

What is external radiotherapy?

Answer 27

Beams of gamma, x-ray or protons directed at tumours from different angles for safety.

Question 28

What is internal radiotherapy?

Answer 28

Beta emitter placed near tumour.

Question 29

What is cure?

Answer 29

Getting rid of symptons of a disease or condition.

Question 30

What is palliative care?

Answer 30

Optimising quality of life and mitigating suffering among people with a complex illness.

Question 31

What is the difference between nuclear fission and fusion?

Answer 31

fission-nuclei break up to produce smaller nuclei and energy(used in power stations)

fusion-two small nuclei fuse to form a larger one(happens on the sun)

Question 32

What is expensive about nuclear power stations?

Answer 32

It is expensive to decommission the waste.

Question 33

What happens in fission?

Answer 33

When a nucleus absorbs a neutron, 2 daughter nuclei are made and 3 electrons are released making it a chain reaction. Energy is transferred by heating. 10,000 times better than coal. Bombs are uncontrolleed but nuclear power stations are controlled.

Question 35

How do nuclear reactors work?

Answer 35

Question 36

Explain examples of fusion and why it is hard to replicate.

Answer 36

Two hydrogen atoms fuse to form helium on the sun. Strong electrostatic repulsion from the positrons has to be overcome. The strong gravitational field of the sun makes this happen due to the extremely high pressure. It is also hot which makes the particles move around more. When the ycolide, a gamma ray and huge amounts of energy are released.

Question 38

Why is nuclear fusion important to live?

Answer 38

It happens on the sun which provides energy, light and heat.

Question 39

What does stable mean?

Answer 39

Dies not emit ionising radiation.

Question 40

What is the role of the moderator?

Answer 40

The moderator helps slow down the neutrons produced by fission to sustain the chain reaction. Control rods can then be inserted into the reactor core to reduce the reaction rate or withdrawn to increase.