P4 - Radiation For Life

Question 1

Explain how static electricity is used in electrostatic dust precipitators to remove smoke particles etc from chimneys:

Answer 1

1. High voltage metal grids put into chimneys to produce a charge on the dust. 2. Dust particles gain or lose electrons. 3. Dust particles induce a charge on the earthed metal plate 4. Plates struck, dust falls to collector.

Question 2

Explain how static electricity is used in paint spraying.

Answer 2

1. A spray gun gains or loses electrons to become positively or negatively charge. 2. As a result, the dust particles are negatively or positively charged. 3. Because paint particles have same charge, they repel each other and form fine consistent spray/coat. 4. The dust particles induce an opposite charge on the object (i.e. the car loses or gains electrons). 5. As a result, the dust particles are attracted to the surface of the object, meaning even the ‘shadows’ of the object are painted. As a result, we have an even coat with less waste.

Question 3

Explain how static electricity can be useful for restarting the heart when it has stopped (defibrillator):

Answer 3

1. Paddles are charged. 2. There is electrical contact between paddles and patient’s chest. 3. Charge passed through patient to make heart contract. 4. Care taken to ensure operator/doctor is not shocked.

Question 4

What is resistance measured in?

Answer 4

Ohms

Question 5

What colour is the live wire?

Answer 5

Brown

Question 6

What colour is the earth wire?

Answer 6

Yellow + Green

Question 7

What colour is the neutral wire?

Answer 7

Blue

Question 8

What is a resistor?

Answer 8

A component that reduces the current flowing in a circuit.

Question 9

What is a variable resistor?

Answer 9

A resistor whose resistance can be changed/reconfigured.

Question 10

Explain how variable resistors can be used to change the current in a circuit:

Answer 10

• Longer wires have more resistance - Thinner wires have more resistance

Question 11

Describe the relationships between current, voltage (pd) and resistance:

Answer 11

• For a given resistor, current increases as voltage increases and vice versa. - For a fixed voltage, current decreases as resistance increases and vice versa.

Question 12

What is the equation for resistance?

Answer 12

resistance = voltage / current

Question 13

What is the function of the live wire?

Answer 13

• Carries the high voltage

Question 14

What is the function of the neutral wire?

Answer 14

• Completes the circuit

Question 15

What is the function of the earth wire?

Answer 15

• Safety wire to stop appliance from becoming live.

Question 16

Explain how a wire fuse reduces the risk of fire; if the appliance develops a fault:

Answer 16

• If current becomes too large, the fuse melts. - This prevents the flow of current. - This prevents overheating and potential fire. - In turn, this prevents further damage to appliance.

Question 17

Why don’t double-insulated appliances need a fuse?

Answer 17

Since the appliance is made out of an insulative material, it can’t carry an electrical current. As a result, there is no risk of the appliance becoming live.

Question 18

What type of wave is ultrasound?

Answer 18

Longitudinal

Question 19

What is a rarefaction?

Answer 19

A region of lower pressure.

Question 20

What is a compression?

Answer 20

A region of higher pressure.

Question 21

Why can’t we hear ultrasound waves?

Answer 21

The frequency of ultrasound waves (20,000 Hz) is much higher than the upper threshold of human hearing.

Question 22

How is ultrasound used in body scans?

Answer 22

1. Device emits ultrasound waves. 2. These waves travel the body, but some of the ultrasound waves are reflected back when they reach a boundary between two different media (e.g. the fluid in the womb and the skin of the foetus). 3. Depending on the depth of this boundary, the ultrasound waves are reflected back at different times. 4. The receiver picks up these returning ultrasound waves and uses their sequence and distribution to produce a video image of the thing being scanned.

Question 23

How is ultrasound used to help get rid of kidney stones?

Answer 23

1. Ultrasound beam concentrated high energy wave at kidney stones. 2. Kidney stones break down into smaller, finer pieces. 3. As a result, the stones can pass out more easily via the patient’s urine. 4. This is non-invasive surgery.

Question 24

What are the advantages of ultrasound scans over x-rays?

Answer 24

• Ultrasounds can produce images of soft tissues, whereas x-rays can only produce image of bones. - Ultrasounds don’t ionise and damage skin cells.

Question 25

What is ionisation?

Answer 25

Particles gain or lose electrons to become charged.

Question 26

What is the half-life of a radioactive substance?

Answer 26

The time it takes for the radioactivity of that substance to halve.

Question 27

Why are alpha particles such good ionisers?

Answer 27

• They’re relatively large, so it’s easy for them to collide with atoms or molecules. - They’re highly charged meaning they can easily remove electrons from the atoms they pass or collide with.

Question 28

Where does radioactivity come from?

Answer 28

The nucleus of an unstable atom.

Question 29

What is an alpha particle?

Answer 29

A helium nucleus

Question 30

What is a beta particle?

Answer 30

A fast moving electron

Question 31

Describe what happens to a nucleus when an alpha particle is emitted:

Answer 31

• mass number decreases by 4 • nucleus has two fewer neutrons • nucleus has two fewer protons • atomic number decreases by 2 • new element formed.

Question 32

Describe what happens to a nucleus when a beta particle is emitted:

Answer 32

• mass number is unchanged • nucleus has one less neutron • nucleus has one more proton • atomic number increases by one • new element formed.

Question 33

Describe how tracers are used in industry:

Answer 33

• A radioactive tracer is put into the pipe. - A detector is used to track the tracer above ground. - A leak or blockage can be shown by a reduction in the levels of radioactivity after a certain point (the point of blockage/leakage).

Question 34

Explain how a smoke detector with an alpha source works:

Answer 34

1. Alpha source between two electrodes ionises air particles allowing a current to flow. 2. When smoke enters alarm, the smoke particles are hit by the alpha radiation instead. 3. As a result, less ionisation of the air particles. 4. Therefore, the current is reduced, causing the alarm to go off.

Question 35

Explain how measurements of the activity of radioactive carbon can lead to an approximate age for different materials:

Answer 35

• The amount of carbon-14 in the air has not change over time. - Furthermore, objects don’t take in anymore carbon-14 when they’re dead as gaseous exchange has stopped. - As the remaining carbon-14 decays, its radioactivity decreases. - Therefore, we can analyse the radioactivity of the carbon-14 in a dead organism (e.g. a tree) to calculate an approximate age based on the half-life of carbon 14.

Question 36

What are the similarities between X-rays and gamma rays?

Answer 36

• They are both ionising electromagnetic waves - They have similar wavelengths

Question 37

What is the difference between X-rays and gamma rays?

Answer 37

They are produced in different ways.

Question 38

How are medical radioisotopes produced?

Answer 38

Materials are placed inside a nuclear reactor.

Question 39

Why are X-rays easier to control than gamma rays?

Answer 39

Gamma rays are produced as a result of the completely random nuclear decay of some elements - this radioactivity cannot be controlled. On the other hand, X-rays are produced by firing high-speed electrons at metals; this can be controlled.

Question 40

How are images produced via X-rays?

Answer 40

The thicker or denser the material, the more x-rays that are absorbed by it. As a result, the differing levels of absorption by different materials (bones) in our body can be used to create an image.

Question 41

How are gamma rays used to treat cancer?

Answer 41

• Gamma rays are focused on the tumour using a wide beam. - This beam is rotated around the patient with the tumour at the centre. - As a result, non-cancerous cells are not targeted by the gamma rays and are therefore not killed.

Question 42

How is gamma or beta radiation used in medical tracers?

Answer 42

1. Beta or gamma source chosen with short half-life. 2. Source ingested/injected by patient. 3. The source is then allowed to spread throughout the body. 4. The radioactivity can then be followed using a tracer to identify issues within the body.

Question 43

Why can only gamma (and sometimes beta) emitters be used as medical tracers?

Answer 43

Alpha radiation cannot penetrate through material, meaning it won’t be able to pass out of the body and be detected.

Question 44

Why are emitters with short half-lives chosen as medical tracers?

Answer 44

Tracers need to have a short half-life so that the radioactivity inside the patient’s body disappears quickly. If it didn’t, there would be a long-term risk of ionisation of healthy cells.

Question 45

What is the difference between nuclear fission and nuclear fusion?

Answer 45

Nuclear fission is the splitting of nuclei. Nuclear fusion is the joining of nuclei.

Question 46

How is electricity generated at a nuclear power station?

Answer 46

• There’s a nuclear reaction that produces lots of heat energy. - That heat energy is used to boil water and produce steam. - Steam is used to spin a turbine. - This drives a generator, that produces electricity.

Question 47

Describe what happens to allow uranium to release energy.

Answer 47

• Uranium nucleus is hit by a slow-moving neutrons. - Uranium absorbs extra neutrons and becomes unstable. - Uranium then splits into two smaller nuclei. - Lots of energy released - 2 or three fast moving neutrons are also released

Question 48

Explain what is meant by a chain reaction.

Answer 48

• When the uranium splits, it releases 2 or three fast-moving neutrons. - These neutrons can then cause further uranium nuclei to split, which will again cause the release of more neutrons, e.c.t.

Question 49

How can a chain reaction be controlled?

Answer 49

• Boron control rods placed in reactor - These control rods absorb some of the neutrons to limit the chain reaction. - However, the control rods are used in a size and quantity so that enough neutrons remain to allow the reaction to continue going. - As a result, the chain reaction continues, but happens without spiraling out of control and without causing the reactor to overheat.

Question 50

How does nuclear fusion release energy?

Answer 50

• Fusion happens when two nuclei join together. - Fusion produces large amounts of heat energy. - Fusion happens at extremely high temperatures

Question 51

Why is fusion difficult for power generation?

Answer 51

It requires extremely high temperatures that are difficult to safely manage and control.

Question 52

Describe how two hydrogen nuclei can join together in a fusion reaction.

Answer 52

A hydrogen-1 nucleus combines with a hydrogen-2 nucleus to form helium-3

Question 53

What conditions are needed for nuclear fusion to take place? How does this relate to its potential uses?

Answer 53

1. In stars, fusion happens at extremely high temperatures and pressures.
2. In fusion bombs, a fission reaction is intially needed to create the exceptionally high temperatures needed for fusion
3. It is very hard to carry out fusion for power generation as the huge pressures and temperatures needed pose big safety problems.

Question 54

Why is fusion research carried out as an international joint venture?

Answer 54

By sharing resources between teams from different countries, the costs of research can be reduced dramatically. Furthermore, a greater pool of expertise and experience is available to make new discoveries.

Question 55

Why was data from cold fusion experiments shared between scientists?

Answer 55

So that other scientists could repeat the experiment and test the initial conclusions drawn.

Question 56

Why is ‘cold fusion’ still not accepted as reliable/realistic method of energy production?

Answer 56

Few scientists were able to successfully repeat the initial cold fusion experiments to produce reliable results. As a result, there is lots of scepticism around cold fusion as a realistic method for energy production.