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Physics > Topic 11 - Radioactivity > Flashcards

Topic 11 - Radioactivity Flashcards

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1
Q

Ionisation

A

Process by which electrons can be added or removed from an atom to create an ion

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2
Q

Types of ionising radiation

A

Alpha (α), Beta (β) and Gamma (γ)

These are emitted from unstable nuclei in a random process

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3
Q

Alpha (α)

A
  • Most ionising
  • Least penetrating
  • Middle activity
  • Blocked by paper, aluminium and lead
  • Particle is a helium nucleus
  • +2 charge
  • mass of 4
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4
Q

Beta (β)

A
  • Moderate ionising
  • Moderate penetrating
  • Highest activity
  • Blocked by aluminium and lead
  • Particle is a fast-moving electron
  • -1 charge
  • mass of 1/2000
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5
Q

Gamma (γ)

A
  • Least ionising
  • Most penetrating
  • Lowest activity
  • Blocked by lead
  • An EM wave
  • No charge
  • No mass
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6
Q

Penetration powers practical

A
  • Set up Geiger-Muller tube and counter
  • Measure background radiation in 10 seconds
  • Place source in front of detector (use gloves and tweezers)
  • Measure count rate in 10 secs and take background radiation away
  • Place materials in order, paper then aluminium then lead
  • Count rate will significantly decrease if radiation is stopped
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7
Q

Effect on atomic and mass numbers (alpha decay)

A
  • 2 protons and 2 neutrons are lost (helium nucleus)
  • Mass number decreases by 4
  • Atomic number decreases by 2
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8
Q

Effect on atomic and mass numbers (beta decay)

A
  • neutron is converted into a proton and an electron
  • mass number is unchanged
  • atomic number increases by 1
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9
Q

Effect on atomic and mass numbers (gamma decay)

A
  • Energy is lost from an atom in the form of an electromagnetic wave
  • Mass number is unchanged
  • Atomic number is unchanged
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10
Q

Effect on atomic and mass numbers (neutron decay)

A
  • neutron is emitted
  • mass number decreases by 1
  • atomic number unchanged
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11
Q

Photographic film

A

radiation causes photographic film to darken

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12
Q

Background radiation

A

The radiation that is naturally found in the environment and exists around us all the time

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13
Q

Sources of background radiation

A
  • Radon gas (50%)
  • Rocks and building materials (15%)
  • Medical (e.g. X-rays) (13%)
  • Food (11%)
  • Cosmic rays (10%)
  • Other (1%)
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14
Q

Nature of activity of radioactive sources

A
  • Decreases over a period of time
  • Measured in Becquerels (Bq)
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15
Q

Activity

A

The rate at which the unstable nuclei from a source of radiation decays

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16
Q

Half-life

A

The time it takes for the number of nuclei of the isotope in a sample to halve

17
Q

Calculating half-life graphically

A
  • find the starting number and halve
  • draw a line going across from that value until the trend line is reached
  • draw a line down to the time
18
Q

Ionisation smoke alarm

A

without smoke: alpha particles knock electrons free from air molecules, causing them to flow to the positive plate, creating a small current

with smoke: smoke particles attach to ions, rendering them neutral, disrupting the flow of current and initiating the alarm

19
Q

Uses of radioactivity

A
  • diagnosis and treatment of cancer
  • sterilising food
  • sterilising medical equipment
  • determining age of artefacts
  • checking thickness of materials
  • smoke detectors
20
Q

Contamination

A

when an object has a radioactive material introduced INTO it

object becomes radioactive and emits radiation

21
Q

Irradiation

A

when an object is exposed to a source of radiation OUTSIDE the object

object is exposed to radiation but does not become radioactive

22
Q

Dangers of ionising radiations

A
  • radiation can cause mutations in living organisms
  • radiation can damage cells and tissue
23
Q

Disposal of radioactive waste

A
  • an isotope may have a long half-life, meaning a sample of it will decay slowly
  • it will remain radioactive for a very long time, therefore presenting risk of contamination for longer
  • it is buried underground to prevent it from being released into the environment
24
Q

Ionising radiation

A

Radiation that is able to remove electrons from atoms or molecules to produce cations.

Physics (8 decks)

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