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Physics > P7-Radioactivity > Flashcards

P7-Radioactivity Flashcards

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1
Q

Atoms are very small , what is the radius of an atoms .

A

1*10to the power of negative 10

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2
Q

What is the radius of a nucleus ?

A

-Less than 1/10,000 of the atom .

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3
Q

Where is most of the mass of an atom

A

-concentrated in the nucleus .

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4
Q

What does the nucleus contain , so what is its charge ?

A

Protons postive charge , ad neutrons no charge so overall charge of nucles is positive .

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5
Q

Electrons

A

negatievly charged found at fixed energy levels form the nucleus .

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6
Q

Energy levels that are further form the nucleus …

A

are at a higher energy than those which are close to the nucleus .

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7
Q

If an atom absorbs electromagnetic radiation-light-…

A

an electron can move from a lower energy level to a higher energy level .
-An atom can now emit electromagnetic radiation , returns to the lower energy level .

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8
Q

What is the mass number?

A

number of protons and neutrons

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9
Q

What is the atomic number ?

A

protons - all atoms of an elemnt have same protons or it isn’t that elemnt .

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10
Q

What is the charge of an atom ?

A

No charge
-As the numbero f electons are = to the nuumber of protons .

(The negative charges on the electrons cancel out positive charged on the protons )

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11
Q

How do you work out the number of neutrons ?

A

Mass Number - Atomic Number .

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12
Q

What are Isotopes ?

A

-Atoms of the same elemnt thata have different number of neutrons .

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13
Q

What are ions

A

electrically charged particles formed when atoms gain or loose elctrons .
-Atoms can loose electrons from their out energy elvels .

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14
Q

Atoms loose an electron…

Atoms gains an electron

A

1+charge

1- charge

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15
Q

What did the ancient Greeks believe everything was made of ?

A
  • Evertyhing is made of atoms .

- Thought atoms were tiny spheres which cannot be divided .

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16
Q

What did scientists discover in 1897 ?

A
  • Atoms contain tiny negative particles . They are called electrons .
  • This showed atoms are not spherres that cannot be divided , atoms have an internal structure .
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17
Q

Plum pudding model :

draw ad explain .

A

-An atom is as a ball of positive charge with negative elctrons embedded in it . Check sheet .

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18
Q

Why was the Alpha Scattering experiment done ?

A

To see if the plum pudding model was correct .

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19
Q

What is the first step of the alpha scattering experiment .

A

Take a place of gold foil.

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20
Q

Why was gold foil used ?

A

-Gold foil was used s it can be hammered down into very thin foil , just a few atoms thick .

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21
Q

What is the second step of the alpha scattering experiment ?

A

Then they fired tiny alpha particles at the gold foil .

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22
Q

What was the first observation of the alpha particle experiment ?

A

-Most of the alpha particles passed straight through the foil without changing direction .

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23
Q

What was the second observation of the alpha particle experiment ?

A

-Sometimes an alpha particle was deflected .

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24
Q

What was the third observation of the alpha particle experiment ?

A

-Sometimes an alpha particles bounced straight back off the goild foil .

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25
Q

What does the first observation suggest ?

A

-Atoms are mainly empty spacce .

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26
Q

What does the second observation suggest ?

A

-The center of the atoms must hve had a posiitve charge that repelled the alpha particles .

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27
Q

What does the third observation suggest ?

A

-The mass of the atom must be the concentrated center , we now call this paert of an atom the nucleus .

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28
Q

what was the final conclusion to the plum pudding model ?

A

-replaced with the nuclear model .
Tiny positive nucleus
Mostly empty space
negative lectron around the edge .

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29
Q

What did Niels Bohr do ?

A
  • Electrons orbit the nucleus at speicifc disances , his work agreed with other sicenitsts
  • We now call the “Orbits” energy levels or shells .
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30
Q

Wha did James Chadwick do ?

A
  • several years later , positive chargge in nuncleus so called protons .
  • years after nuclar model , James Chadwick discovered neutrons , said they have no charge , are neutral .
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31
Q

Some isotopes have an unstbale nucleus , what do they do to become stable , and what is this called ?

A
  • To become stable , the nucleus gives out radiation , this is known as radiactive decay .
  • Radioactive decay is a random process .
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32
Q

What is the activity ?

A

The activity is the rate at which a source of unstable nuclei decay .

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33
Q

What is activity measrued in ?

A

In Becquerel (Bq) 1Bq is = s decay per second .

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34
Q

What is the countrate ?

A

Is the number of deays recorded each second by a detector .

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35
Q

What are alpha particles ?

A

-Consist of two protons and two neutrons same as a helium nucleus .

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36
Q

What are Beta particles ?

A

-A beta particle is an electorn ejected from the nucleus at a very high speed.

37
Q

How is an electrons ejected form the cenetr whne htere is no electrons in the center ?

A
  • Beta particle formed inside the nucleus when a neutron changes into a proton and an electron . This is now ejected rom thhe nueclues and is called a beta particle .
38
Q

What is Gamma radiation ?

A

-Gamma rays are a type of electromagentic radiaition from the nucleus .

39
Q

What is the last time of radiaition sometimes given out by the nucleus ?

A

A neutron

40
Q

What is the range of alpha particles ?

A

-Alpha particles are large , They can travel around 5 cm in air before they collide with air particles and sotp .

41
Q

What is the range of Beta particles ?

A

-Can travel further than alpha particles as they smaller than em too . Can reach 15cm before stopping .

42
Q

What is the range of Gamma radiation ?

A

-Travels severeal metres in air before stopping , longest range .

43
Q

Penetrating power of alpha .

A

-stopped by a single sheet of paper .

44
Q

Penetrating power of Beta .

A

-stopped by a few milimetries of aluminium .

45
Q

Penetraitng power of Gamma radiation ?

A

-Even harde rto stop , stopped bys everal cm lead or concrete .

46
Q

WHat is ionsiing power of radiation ?

A

-When radiaition collides with atoms , causes atoms to lose electrons to form ions .

47
Q

Ionsising power of alpha

A

Very strongly ionsing

48
Q

Ionsiing power of Beta

A

Quiet strongly ionsing

49
Q

Ionising power of Gamma

A

Weakly ionising

50
Q

What is half life ?

A

-half life of a radiactive isotope is the time it takes for the number of nuclei in the isotope of a sample to halve .

51
Q

half life

A

short hlf lfie -fast decay to half

Lon half life - slow decay to half .

52
Q

What is the second definiton of half life?

A

Half life is also the time it takes for the countrate (or activity) of a sample containing the isotope to half its inital level .

53
Q

A radioactive isotope has a half life of 15 days and an initial countrate of 200 days per second . What is its countrate in 45 days , show full working out /

A

25 counts/s

54
Q

Why is ionising radiation dangerous ?

A

-Ionsing radiaiton can increase hte irsk of cancer in humans .

55
Q

What is irradiation ?

A
  • Exposing an object to nuclear radiation (alpha , beta , gamma or neutrons ) e,g for sterilisation.
  • Most sterilistion can be done by heating but for substances that can’t be heated use gamma radiation .
56
Q

How do you sterilise a syringe ?

A
  1. Object neededing to be sterilised is placed in a plastic wrapper stopping bacteria from enetering .
    2.Place object near radioactive isotope tgar emits gamma radiaitoin .
    Lead shield protects workers .
    4.Withdrawing the lead shield allows gamma radiation irradiate the object , the gamma radiaition kills any bacteria .
57
Q

How does the obeject during sterilisation not become radioactive ?

A

As the object itself is not in contact with the radioactive isotope only the radiation emited from it .

58
Q

What precautions do you have to take for each radioactvite sustances ?

A

*-Alpha , not very penetrating , so gloves .
Beta and Gamma - more penetrative , lead apron can stop .
High levels of radiation - lead walls , lead glass windows .

59
Q

What is another way to reudce exposure to radiation ?

A

By monitoring radiation with a raidiation monitor , we can measure how much radiation has been recieved , cannot sotp though .

60
Q

What is radioacitve contamination ?

A
  • When unwated radiactive isotopes end up on other materials .
  • This is hazardous as radioactive toms decay and emit ionisng rdiation .
61
Q

How hazardous is alpha radiation ?

A

-Alpha is strongly ionsing , easily stopped by skin as it is not very penetrative , HOwever can be dangerous if inhaled or swallowed .

62
Q

How hazardous is Beta radiation ?

A

-Quet ionisng , easily penetrate skin and inot the body damage the cell and DNA .

63
Q

How hazardous is Gamma radiation ?

A

Least damaging as it is weakly ionsing , can penetate the body , but is likely to pass straight thorgh you .

64
Q

Peer review on the effects of radiation ?

A
  • Scientists have explored the effects of radiation on human .
  • Studies have to be published and shared with other scientists allowing findings to be checked.
65
Q

What is Background radiation ?

A

Radiaion all around us all the time .

66
Q

Give one natural source of background radiation ?

A

-Rradioactive rockk - certain rocks are radiactive granite .

67
Q

Give another natural source of background radiation ?

A

Cosmic rays from space - Cosmic rays are very high energy particles which travel through space and crsh into the Earth’s atmospehre .

68
Q

Give one source of manmade background radiation ?

A

Nuclear weapon testing - has released radiactive isotopes into the environment for decades.

69
Q

Give another source of manmade background radiation ?

A

Nuclear accidents - Radioactive isotopes are released by accdients at nuclear power stations .

70
Q

What is your exposure to background radiation influenced by ?

A

-Your locatin (Cornwall -rocks) and Occupation (Cabin crew , cosmic trays )

71
Q

What is radiation dose measured in

A

Sievert (Sv)

-One millisievert (mSv) is 1/1000 of a Sievert .

72
Q

What is the first use of nuclear radiation in medicine ?

A

-Exploring internal organs using a radioactive source to check whether an organ is funcitioning normally or if a cancer has developed .

73
Q

What does radioacitve iodine do ?

A
  • Radioactive iodine is a type of gamma radiatio , passes out the body , can be detected .
  • If the scan shows the thyroid has absorbed tooo much or too little iodine , doctors can use this to dianose pateints condtiions .
74
Q

What is the first requirement of a radioactive tracer ?

A

1.The tracer must emit radiaition that can pass out the body and be detected (gamma or beta radiation ).

75
Q

What is the second requirement of a radioactive tracer ?

A

2.The tracer must not be strongly ionisng , to minimise damage ot body tissues .

76
Q

What is the third requirement of a radioactive tracer ?

A

-The tracer must not decay into another radioctive isotope .

77
Q

What is the fourth requirement of a radioactive tracer ?

A

-The tracer must have a short-half lfie , so it is not present in the body for a long period .

78
Q

Cancer cells ?

A

-Certain cancer cells can be destroyed using ionisng radiation - radiotherapy .

79
Q

How does radiotherapy work ?

A

Rays pass into the body and destroy the tumour

80
Q

Probelm with radiation on the outside ?

A

Healthy tissue may also be damaged as radiaition passes throguh the body .

81
Q

Advanatge of radiation in the inside ?

A

Radiation is targeted very precisiely to the tumour , less damage to healthy tissue .

82
Q

What is nuclear fission ?

A
  • Some elements have large and unstable nucelueses .

- In nuclear fission , the nuceus of these element split , due to absorbtion of NEUTRON .

83
Q
  1. Stage of nuclear fission ?
A

-When uranium absorbs a neutron , this triggers the nucleus to undergo fission (split).

84
Q
  1. Stage of nuclear fission ?
A
  • When the nucleus splits , it forms two smaler nuclei roughly euqal in size (daughter nuclei ).
  • Also emit two or three neutrons and gamma radiaition .
85
Q

3.What is also released from nuclear fission .

A
  • Energy is also released during fission , fission products have kinetic energy .
  • These neutrons can be absorbed by more uranium nuclei and trigger ufsion again known as a CHAIN REACTION .
86
Q

Example of a controlled chain reaction .

A

-Used to release energy in a nuclear reactor .

87
Q

Example of an uncontrolled chain reaction ?

A

The explosion of a nuclear weapon .

88
Q

What is nuclear fusion ?

A
  • Two light nuclei are joined to form a hevaier nucleus .

- Some of the mass of the nuclei can be converted into energy which is released as radiation . Not A CHAIN REACTION .

89
Q

What is a nuclear reactor label parts of it

A

-where controlled fissionr eactions occur .
-Control rods - control the number of neeutrons gthat start new fisisn reactions .
-Fuel rolds ontin thematerial that relese energy during fisison .
-eacotr is where fission occurs , releses energy to het up th emoderator for electriciy generation .
-Moderator - slowd down the netrons for new fision rwactions .

Physics (20 decks)

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