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Year 11 Additional Physics > Radioactivity > Flashcards

Radioactivity Flashcards

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1
Q

What did Rutherford and his pal do to prove the plum pudding method wrong?

A
  • Fired a beam of Alpha particles at thin gold foil
  • Expected it too be slightly reflected
  • Most particles went straight through, an odd one came back
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2
Q

What did Rutherford show?

A
  • Most of the mass is concentrated at the centre of a tiny nucleus
  • Nucleus must be positively charged as it repelled the positively alpha by large angles
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3
Q

What is in the nucleus?

A

Protons and neutrons

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4
Q

The radius of the atoms nucleus is about ….. times …… than the radius of the atom

A

10,000

Smaller

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5
Q

What is the Mass of the Proton, electron and neutron

A 
P = 1
N = 1
E = 1/200 (zero)
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6
Q

What is the Charge of the Proton, electron and neutron

A 
P = +1
N = 0
E = -1
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7
Q

Number of protons equals

A

The number of electron

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8
Q

The charge of an electron is

A

The same size as the charge on a proton but opposite

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9
Q

Number of protons =

A

The number of electrons in a neutral form

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10
Q

What is an isotope

A

An element which has the same amount of protons but different neutrons

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11
Q

When does Radioactivity happen?

A

Its random, you cant say when one is going to decay

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12
Q

What is background radiation?

A

It is radiation that is present at all times

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13
Q

Where does the background radiation we receive come from?

A
  • Naturally occurring unstable isotopes (in the air, food, building materials, rocks)
  • Radiation from space (Cosmic rays)
  • Radiation from man made sources (fallout from nuclear weapons tests, nuclear accidents, dumped nuclear waste)
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14
Q

How can radiation effect you?

A
  • Underground rocks
  • High altitudes (jet planes)
  • Underground (mines)
  • Nuclear industry
  • Radiographers in hospitals
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15
Q

Alpha particles are

A

Helium nuclei (Two neutrons and protons)

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16
Q

Beta particles are

A

Electrons

With virtually no mass and a charge of -1

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17
Q

Gamma rays are

A

Very short wavelength EM waves

18
Q

Alpha particles are..

A

Big, heavy and slowing moving

They don’t penetrate very far in materials and stop quickly

19
Q

Beta particles are..

A

Quite fast moving, quite small

They penetrate moderately into materials before cooling

20
Q

Gamma rays..

A

Penetrate far into materials without being stopped and pass straight through air

21
Q

Because of their size alpha particles…

A

Strongly ionising - they bash into a lot of atoms and knock electrons off them before slowing down

22
Q

For every B particle emitted…

A

A neutron turns to a proton in the nucleus

23
Q

What is the mass and charge of gamma rays

A

There is no mass or charge

24
Q

What are alpha and beta particles deflected by

A

Electric and magnetic fields

25
Q

What is the charge of Alpha and beta particles

A 
A = Positive charge 
B = Negative charge
26
Q

What do alpha and beta particles deflect in different directions?

A

Because of their opposite charges

27
Q

Why do alpha particles deflect less?

A

Because of their greater mass

28
Q

Why do gamma rays not deflect?

A

Because they have no charge

29
Q

Half-life

A

The average time it takes for the number of Nuclei in a radioactive isotope sample to halve

30
Q

What happens each time decay happens

A

An alpha, Beta or gamma is given out

31
Q

The older the sample…

A

The less radiation it will emit

32
Q

Short half-life

A

The activity falls quickly, because lots of the nuclei decay quickly

33
Q

Long half-life

A

The activity falls more slowly, because most of the nuclei don’t decay for a long time - they sit their unstable

34
Q

If the initial amount is 640. What is one half-life

A

320

35
Q

If the initial amount is 340. What is two half-life

A

160

36
Q

If the initial amount is 340. What is three half-life

A

80

37
Q

In the example 2 hours represents three half-lives so the half life is

A

120/30 = 40 minutes

38
Q

Name 4 uses of radiation

A

Smoke detectors
Tracers in medicine
Radiotherapy
Sterilisation

39
Q

What radiation do smoke detectors use

A

Alpha

  • A weak source is placed close to two electrons
  • The source causes ionisation and a current flows between the electrodes
  • If a fire occurs the smoke will absorb the radiation -> alarm sounds
40
Q

What radiation do tracers in medicine use

A

Beta or gamma

Year 11 Additional Physics (2 decks)

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