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Edexcel IGCSE Physics > Radioactivity > Flashcards

Radioactivity Flashcards

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1
Q

In nuclear notation, what is the top number and what is the bottom number?

A
  • Top number is the mass number (no. of protons + no. of neutrons)
  • Bottom number is the atomic number which determines the element (no. of protons)

Unless it is an ion, the number of protons will be equal to the number of electrons

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2
Q

What does ionisation mean?

A

The gain or loss of electron(s) in order to form an ion

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3
Q

What is an isotope?

A

An atom with the same number of protons but a different number of neutrons

Isotopes occur naturally, but some are more rare than others

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4
Q

Why do some nuclei emit radiation?

A
  • Because they are unstable as they are isotopes which are too big and/or have too many or too few neutrons
  • They emit radiation to become more stable

Radioactive decay is a random (unpredictable) process

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5
Q

What are the three types of nuclear radiation that can be emitted from unstable nuclei?

A
  • Alpha
  • Beta
  • Gamma
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6
Q

What does an alpha particle released from an unstable nucleus consist of?

A

Two protons, and two neutrons (+2 charge)

It is the same as a helium nucleus

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7
Q

What does a beta particle released from an unstable nucleus consist of?

A

One electron (-1 charge)

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8
Q

What does gamma radiation released from an unstable nucleus consist of?

A

High energy electromagnetic waves (gamma rays)

Gamma rays have no charge so cannot be affected by electromagnetic fields

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9
Q

What is the order of penetrating power between the three types of radiation?

A

Gamma - High (Stopped by 1m of concrete)
Beta - Medium (Stopped by 1cm of Aluminium)
Alpha - Low (Stopped by paper)

Same goes for range and speed

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10
Q

What is the order is ionising ability between the three types of radiation?

A

Alpha - High
Beta - Medium
Gamma - Low

Because alpha radiation has the highest mass, size charge etv. This obviously ties in with penetrating power too

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11
Q

What is the order of mass and size between the three types of radiation?

A

Alpha - High
Beta - Low
Gamma - N/A

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12
Q

When measuring the radioactivity of a source, what property should it have for reliable results?

A

Long half life

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13
Q

What must you take into consideration when measuring the count rate of a source?

A

The background radiation

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14
Q

When is the effect on a nucleus when it emits an alpha particle?

A
  • The mass number decreases by four
  • The atomic number decreases by two, so a new element will be formed
  • The charge decreases by two
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15
Q

What is the effect on a nucleus when it emits a beta particle?

A
  • A neutron is turned into a proton and an electron, the proton is kept and the electron is emitted
  • The mass number stays the same, but the atomic number increases by 1, forming a new element
  • The charge increases by 1
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16
Q

What is the effect on a nucleus when it emits gamma radiation?

A

There is no effect on the nucleus, however it does become less energetic

17
Q

What are the two devices you can use to measure radiation?

A
  • Geiger-Muller Tube/Detector
  • Photographic film
18
Q

What are the natural sources of background radiation?

A
  • Radon gas from radioactive rocks like granite
  • Other rocks and soil which emit radiation
  • Radioactive cosmic rays from the sun
  • Radioactive material in food and drink like potassium-40 in bananas
  • Radiation from carbon-14 in all living materials
19
Q

What are the man-made sources of background radiation?

A
  • Medical uses, like x-rays and radiation therapy
  • Fallout from nuclear weapon testing
  • Nuclear waste and nuclear accidents from power stations
20
Q

What unit is radioactivity measured in?

(The rate at which unstable nuclei decay)

A

Bequerels (Bq)

21
Q

What happens to the activity of a radioactive source overtime and why?

A
  • It decreases
  • This is because each decay reduces the overall number of radioactive particles in the source
22
Q

What is the definition of half life?

A

The time it takes for the number of nuclei/actvity in a sample of a rdioactive sample to decrease by half

  • Half life is different for every isotope because the rate of decay (actvity) is different
  • Sources with short half lives tend to have higher activities
23
Q

How does a smoke detector work?

A
  • A source is placed in the detector, usually alpha and with a long half life as it cannot penetrate the casing of the detector and will ionise the air
  • There will be a current detector as well
  • If smoke enters the detector, the alpha particles will no longer ionise the air as it will be blocked and there will no longer be a current present
  • The drop in current will sound the alarm

It might also be done with a radiation detector, and if a drop in count rate is detected due to the blocking smoke, an alarm will sound

24
Q

How can radiation be used to measure thickness of paper/foil in industry?

A
  • Beta should be used, as it will penetrate the paper, but not penetrate everything including the counter
  • If the thickness of the paper changes, the count rate changes
  • The source should have a long half life to achieve a constant reading
25
Q

How are radioactive sources used in medical tracers?

A
  • A radioactive source will be injected into a patient
  • A radiation detector can measure the activity of the source when inside the body, finding diagnostics like the location of tumours
  • It should be gamma so it can penetrate the body and does not ionise, and should have a short half life so the patient suffers little exposure
26
Q

How can radiation be used in radiotherapy?

A
  • Precise beams of gamma radiation are fired at cancerous tumours, while minimising damage to healthy cells
  • Gamma rays are used as they can penetrate the whole body
27
Q

How can radiation be used to sterilise food and medical equipment?

A
  • The item is irradiated with gamma radiation to kill bacteria
  • It is gamma so that it penetrates the whole item including its packaging and still kills the bacteria
28
Q

What is contamination?

A
  • The unwanted presence of materials containing radioactive atoms
  • This will make the material itself radioactive
29
Q

What is irradiation?

A
  • The process of exposing a material to a specific source of radiation
  • The material itself does not become radioactive, but it can kill living cells on the material
30
Q

What are the dangers of radiation?

A
  • DNA damage/mutation from ionisation, causing cancers and tumours
  • Cell and tissue damage, like skin burns, white blood cell damage etc.
31
Q

What are the problems with disposing of nuclear waste and how can the risks be reduced?

A
  • The radioactive sources can have a long half life and can contaminate areas around it
  • They should be buried deep undergroud, sealed by lead or concrete
32
Q

How can you reduce the risk to your health from radiation?

A
  • Store sources in a lead-lined container with shielding
  • Increase the distance from you and the source by using tongs
  • Reduce time exposed to the source
  • Avoid contact with bare skin and wash yourself after being around it
  • Protective clothing should be worn, like lead-lined apron

Edexcel IGCSE Physics (19 decks)

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