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GCSE Physics (OCR Gateway > P4 - Radiation For Life > Flashcards

P4 - Radiation For Life Flashcards

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1
Q

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

A
  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.
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2
Q

Explain how static electricity is used in paint spraying.

A
  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.
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3
Q

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

A
  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.
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4
Q

What is resistance measured in?

A

Ohms

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5
Q

What colour is the live wire?

A

Brown

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6
Q

What colour is the earth wire?

A

Yellow + Green

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7
Q

What colour is the neutral wire?

A

Blue

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8
Q

What is a resistor?

A

A component that reduces the current flowing in a circuit.

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9
Q

What is a variable resistor?

A

A resistor whose resistance can be changed/reconfigured.

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10
Q

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

A
  • Longer wires have more resistance - Thinner wires have more resistance
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11
Q

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

A
  • For a given resistor, current increases as voltage increases and vice versa. - For a fixed voltage, current decreases as resistance increases and vice versa.
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12
Q

What is the equation for resistance?

A

resistance = voltage / current

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13
Q

What is the function of the live wire?

A
  • Carries the high voltage
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14
Q

What is the function of the neutral wire?

A
  • Completes the circuit
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15
Q

What is the function of the earth wire?

A
  • Safety wire to stop appliance from becoming live.
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16
Q

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

A
  • 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.
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17
Q

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

A

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.

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18
Q

What type of wave is ultrasound?

A

Longitudinal

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19
Q

What is a rarefaction?

A

A region of lower pressure.

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20
Q

What is a compression?

A

A region of higher pressure.

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21
Q

Why can’t we hear ultrasound waves?

A

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

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22
Q

How is ultrasound used in body scans?

A
  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.
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23
Q

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

A
  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.
24
Q

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

A
  • Ultrasounds can produce images of soft tissues, whereas x-rays can only produce image of bones. - Ultrasounds don’t ionise and damage skin cells.
25
Q

What is ionisation?

A

Particles gain or lose electrons to become charged.

26
Q

What is the half-life of a radioactive substance?

A

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

27
Q

Why are alpha particles such good ionisers?

A
  • 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.
28
Q

Where does radioactivity come from?

A

The nucleus of an unstable atom.

29
Q

What is an alpha particle?

A

A helium nucleus

30
Q

What is a beta particle?

A

A fast moving electron

31
Q

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

A

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

32
Q

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

A

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

33
Q

Describe how tracers are used in industry:

A
  • 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).
34
Q

Explain how a smoke detector with an alpha source works:

A
  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.
35
Q

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

A
  • 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.
36
Q

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

A
  • They are both ionising electromagnetic waves - They have similar wavelengths
37
Q

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

A

They are produced in different ways.

38
Q

How are medical radioisotopes produced?

A

Materials are placed inside a nuclear reactor.

39
Q

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

A

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.

40
Q

How are images produced via X-rays?

A

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.

41
Q

How are gamma rays used to treat cancer?

A
  • 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.
42
Q

How is gamma or beta radiation used in medical tracers?

A
  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.
43
Q

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

A

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

44
Q

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

A

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.

45
Q

What is the difference between nuclear fission and nuclear fusion?

A

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

46
Q

How is electricity generated at a nuclear power station?

A
  • 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.
47
Q

Describe what happens to allow uranium to release energy.

A
  • 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
48
Q

Explain what is meant by a chain reaction.

A
  • 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.
49
Q

How can a chain reaction be controlled?

A
  • 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.
50
Q

How does nuclear fusion release energy?

A
  • Fusion happens when two nuclei join together. - Fusion produces large amounts of heat energy. - Fusion happens at extremely high temperatures
51
Q

Why is fusion difficult for power generation?

A

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

52
Q

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

A

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

53
Q

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

A
  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.
54
Q

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

A

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.

55
Q

Why was data from cold fusion experiments shared between scientists?

A

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

56
Q

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

A

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.

GCSE Physics (OCR Gateway (5 decks)

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