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radioactivity Flashcards

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AP® Physics flashcards Physics 101 flashcards
1
Q

mass number

A

-total number of particles in the nucleus an atom

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2
Q

atomic number

A

-the number of protons in an atom

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3
Q

relative mass, charge and location of an electron

A

1/2000, -1, shell

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4
Q

relative mass, charge and location of a proton

A

-0, +1, nucleus

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5
Q

relative mass, charge and location of a nucleus

A

1, 0, nucleus

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6
Q

what is nuclear radiation(ionising radiation)

A

-causes ionising radiation by bashing into atoms and knocking electrons off them
-these atoms then become ions

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7
Q

how is ionising radiation detected

A

-by a Geiger-Muller tube

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8
Q

relationship between distance radiation penetrates before hitting an atom and ionising amount

A

-the further radiation travels before hitting an atom, the less ionising it is

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9
Q

three types of ionising radiations

A

-alpha particles
-beta particles
-gamma rays

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10
Q

what is radioactive decay

A

-nuclei are unstable and radioactive due to imbalance of protons or neutrons in the nucleus
-nuclei emits radiation to become more stable
-these changes are spontaneous and random

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11
Q

features of alpha particles

A

-made up of 2 protons and 2 (4-He) neutrons(big and slow)
-low penetrating power
-high ionising power
-electrically charged(+), are deflected by electric and magnetic fields
-stopped by thick paper
-range in air:5cm

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12
Q

features of beta particles

A

-an electron(emitted from the nucleus of an atom when a neutron turns into a proton and an electron)
-medium penetrating power
-medium ionising power
-electrically charged(-), are deflected by electric and magnetic fields
-stopped by aluminium sheet
-range in air:1m

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13
Q

gamma rays

A

-rays of energy(EM wave), no mass
-high penetrating power
-low ionising power
-no charge
-stopped by thick lead
-infinite range in air

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14
Q

isotope

A

-an atom of the same element that have an equal number of protons but a different number of neutrons

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15
Q

method of investigating penetrating powers of different types of radiation

A
  1. connect Geiger-Muller tube to the counter and measure background radiation over one minute without any sources present
  2. repeat three times and take an average. Subtract this value for all subsequent readings
  3. place radioactive source a fixed distance of 3cm away from the tube and take another reading of count rate over a period of one minute
    take a set of absorbers, with different thicknesses
  4. one at a time, place these absorbers between the source and the tube and take another reading of count rate over a period of one minute
  5. repeat for other radioactive sources
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16
Q

check equations from book

A

.

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17
Q

neutron emission

A

-some isotopes can decay by emitting neutrons

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18
Q

how does a Geiger muller tube work

A

-transmits an electrical pulse to a counting machine each time it absorbs radiation
-this makes a clicking sound/displays the count rate
-the greater the frequency of click/the higher the count rate, the more radiation the Geiger Muller tube is absorbing

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19
Q

natural sources of background radiation

A

-Radon gas from rocks and buildings
-Cosmic rays from space
-carbon-14 in biological material
-radioactive material in food and drink

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20
Q

artificial sources of background radiation

A

-nuclear medicine
-nuclear waste
-nuclear fallout from nuclear weapons
-nuclear accidents

21
Q

why does radon gas from rocks and buildings cause radiation

A

-airborne radon gas comes from rocks in the ground and building materials
-this is due to the presence of radioactive elements, such as uranium,, which occurs naturally in small around of all rocks and soils

22
Q

why does cosmic rays from space cause radiation

A

-sun emits enormous number of protons every second
-some protons enter the Earth’s atmosphere at high speeds
-when they collide with molecules in the air, this leads to production of gamma rays

23
Q

how does carbon-14 of biological material cause radiation

A

-all organic matter contains a tiny amount of carbon-14
-living plants and animals constantly replace the supply of carbon in their systems hence the amount of carbon-14 in the system stays almost constant

24
Q

how does radioactive material food and drink cause radiation

A

-naturally occuring radioactive elements can get into food and water since they are in contact with rocks and soil containing these elemtns
-some foods contains higher amounts such as potassium-40 in bananas
-radioactive material in food is still minuscule and is not a cause for concern

25
Q

how does nuclear medicine cause radiation

A

-nuclear radiation is used in medicine (X-rays, CT scans, etc)

26
Q

nuclear waste

A

-causes nuclear radiation
-dangerous to people handling it

27
Q

nucelar fallout from nuclear weapons

A

-fallout is the residue radioactiv ematerial that is thrown into the air after a nuclear expolision

28
Q

how does nuclear accidents cause radiation

A

-contributes a large dose of radiation to the environment

29
Q

what is the activity of a radioactive source

A

-the rate at which the unstable nuclei decay(measured in Becquerels Bq)
1 Bq = 1 nucleus in the source decaying in 1 second

30
Q

how does activity of a radioactive source vary with time

A

-activit decreases with time as each decay event reduces the overall number of radioactive particles in the source

31
Q

wyh do fluctuations occur in a graph of count rate against time

A

-due to the randomness of radioactive decay

32
Q

define half life

A

-the time it takes for the number of nuclei of a sample of radioactive isotopes to decrease by half

33
Q

how to measure half life

A

-measure the initial activity of the sample
-determine the half-life if the original activity
-measure how the activity changes with time
-the time taken for the activity to decrease to half its original value is the half-life

34
Q

uses of radioactivity

A

-monitoring thickness of materials
-smoke detectors
-medical procedures
-sterilising food
-sterilising medical equipment
-determining age of ancient artefacts

35
Q

how are smoke detectors used by radiation

A

-alpha particles are used in smoke detectors
-alpha radiation will normally ionise the air within the detectors, creating a current
-the alpha emitter is blocked when smoke enters the detectors
-the alarm is triggered by a microchip when the sensor no longer detects alpha

36
Q

how can the thickness of materials be measured using radiation

A

-when a material moves above a beta source, some beta particles will be absorbed, but most will penetrate
-the amount of beta particles passing through the material can be monitored using a detector
-if the material gets thicker, more particles will be absorbed and the count rate decreases, and vice versa

37
Q

how can radiation be used in the diagnosis and treatment of cancer

A

-ionising radiation can kill living cells, some cells are more susceptible to radiation than others
-beams of gamma rays are directed at the cancerous tumour, they can penetrate the body and reach the tumour
-beams are moved around to minimise harm to healthy tissue whilst still begin aimed at the tumour

38
Q

how can food and medical equipment be sterilised using radiation

A

-gamma radiation can be used to sterilise medical equipment
-food can be irradiated in order to kill any microorganisms
-gamma rays are the most penetrating, so can irradiate all sides of instruments

39
Q

contamination

A

-the accidental transfer or a radioactive substance onto or into a material

40
Q

what can contamination cause

A

-small amounts of an isotope in contaminated areas will emit radiation and the material becomes radioactive

41
Q

irradiation

A

-the process of exposing a material to ionising radiation

42
Q

what can irradiation cause

A

-can kill living cells
-will not make it radioactive

43
Q

how can radiation affect humans

A

-radiation can mutate DNA in cells and cause cancer through both irradiation and contamination

44
Q

how can contamination affect humans

A

-if a radioactive source gets inside the human body(inhaling or ingesting)
-internal organs will be irradiated as source emits radiation as it moves through the body

45
Q

how to prevent irradiation

A

-shielding to absorb radiation
-lead-lined suits are used to reduce irradiation for people working with radioactive materials

46
Q

how to prevent contamination

A

-an airtight suit is worn by people working in an area where a radioactive source may be present

47
Q

How does ionising radiation lead to mutations

A

-ionising radiation causes damage to DNA
-the cell can sometimes successfully repair the DNA
-incorrect repairs can cause a mutation
-

48
Q

what types of radiation is more dangerous outside the body and why

A

-highly ionising(alpha)
-likely to cause most harm to living cells inside the body

49
Q

what types of radiation is more dangerous from outside the body

A

-highly penetrating(gamma)
-they can pass through the skin and reach living cells in the body

Physics (7 decks)

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