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Physics > AQA Combined Physics 6.4 > Flashcards

AQA Combined Physics 6.4 Flashcards

Revision for Paper 1

1
Q

What does a short half-life mean?

A

The activity falls quickly due to rapid decay

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2
Q

What is half-life?

A

The time taken for the number of nuclei of a radioactive isotope to halve

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3
Q

Why is radioactive contamination so dangerous?

A

Radioactive particles could get inside the body

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4
Q

What is the hazard of radioactive contamination?

A

The hazard is due to the decay of the contaminating atoms

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5
Q

How can net decline be calculated?

A

1) Find the activity after each half-life
2) Divide the final activity by the inital
3) Multiply by 100 to make a percentage

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6
Q

How can the process of radioactivity be described?

A

Random

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7
Q

What would be the nuclear equation for the decay of Uranium-238

A

238 U - 234 Th + 4 He

92 90 2

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8
Q

How many protons does an atom of the same element have?

A

The same number

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9
Q

How can electron arrangements change?

A
  • Absorption of electromagnetic radiation (higher energy level)
  • Emission of electromagnetic radiation (lower energy level)
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10
Q

Describe the basic structure of an atom

A

A positively charged nucleus orbited by negatively charged electrons

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11
Q

How did Bohr adapt the nuclear model as suggested by Rutherford?

A

Bohr suggested electron orbit the nucleus at specific distances (energy levels)

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12
Q

What was the Plum Pudding model?

A

The atom was suggested to be a ball of positive charge with negative electrons embedded in it

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13
Q

What did Rutherford’s scattering experiment show?

A

The mass of the atom was concentrated in the centre (nucleus) and it was charged

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14
Q

Before the discovery of the electron, what were atoms thought to be (as suggested by Dalton)?

A

Tiny spheres that could not be divided

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15
Q

Describe alpha radiation (structure, penetration, absorption and ionising strength)

A
  • 2 neutrons and 2 protons (like a helium nucleus)
  • They don’t penetrate very far (a few cm in air)
  • Are absorbed by a piece of paper
  • They are strongly ionising
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16
Q

What can a Geiger-Muller tube record?

A

The count-rate (number of radiation decays reaching the device per second)

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17
Q

What is ‘activity’ in terms of nuclear radiation?

A

The rate at which a source of unstable nuclei decays

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18
Q

20 years after the nucleus became scientifically accepted, what did James Chadwick identify?

A

Neutrons

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19
Q

What can nuclear radiation emission change in a nucleus?

A

The mass or the charge

20
Q

What happens to the radioactivity of a source over time?

A

It decreases

21
Q

How can an alpha particle be represented?

A

4
He
2

22
Q

How is nuclear ‘activity’ measured?

A

In becquerels (Bq) where 1 Bq is 1 decay per second

23
Q

What happens to Rn^219^ when it experiences alpha decay?

A

219 215 4
radon —– polonium + He
86 84 2
*Mass and charge both decreased

24
Q

How can a beta particle be represented?

A

0
e
-1

25
Q

What can nuclear equations represent?

A

Radioactive decay

26
Q

Describe gamma radiation (structure, penetration, absorption and ionising strength)

A
  • Waves of electromagnetic radiation
  • Penetrate far into materials
  • Absorbed by thick sheets of lead or metres of concrete
  • Weakly ionising
27
Q

As well as alpha, beta and gamma radiation what else can radioactive substances release?

A

Radioactive substances can release neutrons (as they rebalance their atomic and mass numbers)

28
Q

Some atomic nuclei are unstable - what can the nucleus emit (and in doing so become more stable)?

A

Radiation - a random process of radioactivity decay or the unstable nuclei

29
Q

What is radioactive contamination?

A

The unwanted presence of materials containing radioactive atoms on other materials

30
Q

What happens to the mass or charge of a nucleus when it experiences gamma emission?

A

The mass and charge remain the same

31
Q

What happens to C^14^ when it experiences beta decay?

A

14 14 0
carbon —- nitrogen + e
6 7 -1
*Mass remains but charge increased

32
Q

Describe beta radiation (structure, penetration, absorption and ionising strength)

A
  • A fast moving electron (virtually no mass)
  • Penetrate a few metres in air
  • Are absorbed by a 5mm sheet of aluminium
  • Moderatley ionising
33
Q

Approximately how big is the radius of an atom?

A

Very small - a radius of about 1x10^-10^m

34
Q

What does a long half-life mean?

A

The activity falls slowly due to slow decay?

35
Q

Inside the body what radioactivity source is most dangerous?

A

Alpha

36
Q

What is the overall electrical charge of an atom?

A

No overall charge - electron and proton numbers are equal

37
Q

What is the atomic number?

A

The number of protons in an atom

38
Q

How much smaller is the radius of a nucleus compared with the radius of an atom?

A

1/10,000th the radius of an atom (but contains most of the mass)

39
Q

How are electron arranged around the nucleus of an atom?

A

Electrons are arranged at different distances from the nucleus

40
Q

What happens to an atom if it loses one or more outer electron(s)

A

It becomes a positive ion

41
Q

What is an isotope?

A

Atoms of the same element with different numbers of neutrons

42
Q

What types of ionising nuclear radiation are there?

A

1) Alpha
2) Beta
3) Gamma

43
Q

What is irradiation?

A

Exposing an object to nuclear radiation (the object itself does not become radioactive)

44
Q

Outside of the body what radioactive sources are most dangerous?

A

Beta and Gamma

45
Q

What can the positive charge of a nucleus be subdivided into?

A

Protons

46
Q

What is the mass number?

A

The number of protons and neutrons in an atom

47
Q

What precautions should be taken around hazardous radioactive materials?

A
  • Wearing gloves / using tongs
  • Protective suits
  • Breathing apparatus
  • Limiting exposure time

Physics (4 decks)

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