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Edexcel physics > Topic 6- Radioactivity > Flashcards

Topic 6- Radioactivity Flashcards

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1
Q

What happens when an electron changes orbit?

A
  • if move further from nucleus, atom has absorbed EM radiation
  • if electron falls to lower orbit (closer to nucleus), atoms has emitted EM radiation
  • If electron gains enough energy, can leave atom to form an ion
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2
Q

What is an alpha particle?

A
  • helium nucleus (two protons and two neutrons in nucleus)
  • highly ionising
  • weakly penetrating ( most dangerous in body)
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3
Q

What is a beta particle?

A
  • two forms of beta decay, β⁻ decay & β⁺ decay,
  • beta minus have electrons and beta positive have positrons
  • medium ionising & medium penetration
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4
Q

What is gamma radiation?

A
  • from radioactive decay of atomic nuclei
  • short wavelength
  • low ionising weak penetration
  • short wavelength and high frequency
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5
Q

What is background radiation?

A
  • ## Weak And natural radiation that can be detected from natural / external sources like rocks/space and the environment
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6
Q

Examples of background radiation

A
  • Cosmic rays
  • Radiation from underground rocks
  • Nuclear fallout
  • Medical ray
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7
Q

Ways to measure radioactivity

- photographic film

A
  • Film goes darker when absorbs radiation – more radiation absorbed, darker it gets
  • used as badges by people who work w/ radiation, check how much exposure they’ve had
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8
Q

Ways to measure radioactivity

- Geiger-Muller Tube

A
  • tube can detect radiation
  • when absorbs radiation, transmits electrical pulse to machine, produces clicking sound
  • greater number of clicks the more radiation present
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9
Q

How does a beta minus and beta plus decay?

A

-beta minus
- neutron becomes proton– releases electron
beta plus
- proton becomes neutron – releases positron

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10
Q

What is a half- life?

A
  • time taken for half the nuclei in a radioactive sample to decay
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11
Q

How do smoke alarms work?

A

-Americium is used in smoke alarms
▪It’s an alpha emitter
o so stopped by a few centimetres of air (as it’s weakly penetrating)
o alpha particles ionise air particles and makes them charged so making a current
o If smoke enters air around the alarm, the current drops in the circuit– causing alarm to sound

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12
Q

uses of radioactivity for irradiating food

A
  • Gamma rays transfer energy to bacteria, killing them and sterilising food
    o Also used to delay ripening of fruit
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13
Q

uses of radioactivity for sterilising equipment

A
  • usually gamma, exposed onto equipment to kill all microbes present on equipment, so they’re safe for operations
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14
Q

using radioactivity to trace & gauge thickness

A
  • Beta radiation is mildly penetrating, and can pass through paper
    o source receiver placed either side of paper
    ▪ If there is a drop or rise in received electrons, means thickness of paper has changed – i.e. a defect in the production
    o used inside pipes, w/ detector placed externally, to measure thickness of the walls
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15
Q

using radioactivity to diagnose & treat cancer

A
  • gamma emitter, passes through body and external
    detector can picture where the tracer has collected in the body, can reveal tumours
    o Gamma rays used on tumour, to kill cancer cells
  • exposing rays on healthy cells can cause them to mutate or cause damage
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16
Q

Dangers of a short half-life

A
  • does not remain strongly radioactive, but initially it’s very radioactive, but quickly dies down, so direct radiation exposure from decay is high and intense
    o but presents less of a long-term risk
17
Q

Dangers of long half-life

A
  • remains radioactive for a long period of time
18
Q

Differences in contamination and irradiation

A
  • contamination lasts for a long time, irradiation does not last for a long time
  • in contamination the source of the radiation is transferred to an object, in irradiation the source emits radiation which reaches the object
  • in contamination radioactive dust settles on skin, contaminating it, in irradiation radioactive dusts emits beta radiation which irradiate the skin
19
Q

External treatment of tumours

A
  • beam of gamma radiation rotates around body
    o continually focuses on tumour, only passes momentarily across healthy cells surrounding tumour
    o ensures minimal damage on healthy cells, tumour is most affected
    -takes long time to fully treat tumour, taking multiple visits
    ▪ greater risk of long-term side effects, as radiation passes
    through healthy tissues
20
Q

Internal treatment of tumours

A
  • Radioactive material held within a needle, and injected directly into tumour
    ▪ longer period of time spent in hospital, some radioactive implants are of high radioactivity– you emit radiation
21
Q

Uses of PET scanners in physics

A
  • Radioactive tracer inserted into body
    ▪ tracer tagged to desired chemical, and tracer travels
    in body where the chemical travels
    o scanner records where tracer emits radiation
    o produces 3D visualisation of the body
    ▪ Used to show how effective current treatment is
    ▪ Or to diagnose cancer, epilepsy, Alzheimer’s etc.
22
Q

Describe the isotopes used in PET scans

A
  • made locally, because tracer has short half life of 110 mins
23
Q

What is nuclear fission?

A
  • process of a nucleus splitting into two smaller nuclei after absorbing neutrons, which releases more neutrons
  • can be a source of energy
24
Q

What is radioactive decay?

A
  • when an unstable nucleus decays into two smaller nuclei

- can be a source of energy

25
Q

Describe nuclear power?

A
  • Uranium fuel splits releasing neutrons, they’re absorbed by uranium nuclei, which split –nuclear fission in a chain reaction
  • No carbon dioxide is produced
  • safety risk of radiation leaking, or chain reaction become uncontrollable and causing a meltdown
26
Q

Waste disposal in nuclear power?

A
  • difficult – initially extremely hot, waste needs to be placed deep in ‘cooling ponds’ to cool down, before being stored deep underground
  • can be used for nuclear warheads so is a terrorist risk
27
Q

Describe U-235 in nuclear fission power plants

A
  • absorbs neutrons, and becomes unstable
    o causes it to undergo fission & release energy
    ▪ Forms two ‘daughter’ nuclei
    • products are radioactive, they’re strong gamma emitters –some energy released from fission is held by the daughter nuclei
    ▪ Emitting two or more neutrons as well
28
Q

What is a chain reaction?

A
  • when a nucleus splits, emitting neutrons, & these neutrons cause further fissions, which release more neutrons
29
Q

Moderators in a chain reaction?

A
  • usually water/graphite, and slows down emitted neutrons to be absorbed for further fissions (fast moving neutrons cannot be easily absorbed)
30
Q

Control rods in chain reactions

A
  • boron rods in reactor core, absorbs excess neutrons,

preventing a runaway chain reaction

31
Q

Unit of activity of a radioactive isotope

A

Becquerel (Bq)

32
Q

What is the atomic number

A

The amount of protons and electrons (number on the bottom)

- smallest number

33
Q

What is the atomic mass

A

Amount of protons and neutrons in the nucleus (number at the top)

34
Q

Net decline equation

A

Initial no. - number after X half-lives / initial no.

35
Q

Advantages of nuclear power for generating electricity

A
  • nuclear fuels don’t produce Carbon dioxide
  • doesn’t contribute to global warming
  • fuel is readily available
36
Q

Disadvantages of using nuclear power to generate electricity

A
  • unpopular — seen as very dangerous
  • expensive to commission and decommission stations
  • radioactive waste is difficult to dispose and will remain radioactive for many years
37
Q

Consequences of an uncontrolled chain reaction

A

-rate of fission becomes to high and results in the production of too much energy — can lead to a nuclear explosion

38
Q

How’s electricity produced in a nuclear power station

A
  • reaction releases thermal energy (heat)
  • thermal energy (heat) is used to boil water and then produce steam
  • steam’s then used to turn a turbine which starts the generator

Edexcel physics (9 decks)

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