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AQA GCSE - Physics > 2.6 Radioactivity > Flashcards

2.6 Radioactivity Flashcards

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1
Q

What do radioactive substances emit?

A

Radiation

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2
Q

What did J.J Thomson come up with?

A

The plum pudding model for the discovery of the nucleus

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3
Q

Describe the plum pudding model?

A

A sphere of positive charge with small negative charges throughout

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4
Q

What experiment did Ernest Rutherford conduct with Geiger and Marsden?

A

They fired alpha particles at thin gold foil (only a fee atoms thick)

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5
Q

What observations did Rutherford find in his experiment?

A

Most of the Alpha particles went straight through
Some of the Alpha particles were deflected through large angles
Very few of the Alpha particles were deflected straight back

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6
Q

What did Rutherford conclude from his experiment?

A

The plum pudding model is wrong

The nucleus is very small compared to the rest of the atom containing most of the mass and all of the positive charge

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7
Q

Why did some of the Alpha particles deflect?

A

They were too close to the nucleus and repelled because the particles and the nucleus are both positively charged

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8
Q

What is the charge of Alpha?

A

Positive

+2

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9
Q

What is the mass of Alpha?

A

4

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10
Q

What is the ionisation of Alpha like?

A

Strong

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11
Q

What is an Alpha particle made of?

A

2 protons
2 neutrons
Which is a helium nucleus

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12
Q

How is the penetration of Alpha?

A

Bad

Stopped by paper and a few cm of air

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13
Q

What is the charge of Beta?

A

-1

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14
Q

What is the mass of Beta?

A

Negligible

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15
Q

What is the ionisation of Beta like?

A

Average

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16
Q

What is a Beta particle?

A

An electron

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17
Q

How is the penetration of Beta?

A

Average

Stopped by Aluminium and a few metres of air

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18
Q

What is the charge of Gamma?

A

0

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19
Q

What is the mass of Gamma?

A

0

20
Q

What is the ionisation of Gamma like?

A

Weak

21
Q

What is a gamma wave?

A

A Transverse electromagnetic wave

22
Q

What is the penetration of Gamma like?

A

Very good

Stopped by lead and concrete

23
Q

What happens to gamma in a magnetic field?

A

It is undeflected

24
Q

What happens to Alpha in a magnetic field?

A

Slightly deflected

Opposite to Beta

25
Q

What happens to Beta in a magnetic field?

A

Larger deflection

Opposite to Alpha

26
Q

Why do alpha and beta particles go in opposite directions in a magnetic field?

A

They have opposite charges?

27
Q

Why is alpha deflected less than beta in a magnetic field?

A

Alpha has a larger mass

28
Q

What happens to the new product in Alpha decay?

A

Mass number goes down by 4

Proton number goes down by 2

29
Q

What happens to the new product in Beta decay?

A

Mass number stays the same

Proton number goes up 1

30
Q

How can a beta particle be emitted if there are no electrons in the nucleus?

A

A neutron is turned into a proton and an electron

Therefore the electron can be emitted as a beta particle

31
Q

How is the mass number the same in Beta decay?

A

The loss of a neutron but the gain of a proton balances out to the original number

32
Q

What are the origins of background radiation?

A 
Cosmic radiation from space
Nuclear weapon testing 
Nuclear accidents (power stations)
Food (banana)
Sun
33
Q

What categories can origins of background radiation be put into?

A

Natural

Manmade

34
Q

What is half life?

A

The time it takes for the number of radioactive nuclei in a sample or count rate to decrease by 50%

35
Q

How do we measure radioactivity?

A

By measuring the count rate

36
Q

How does radioactive decay occur?

A

It is random

You can’t do anything to make a radioactive substance decay

37
Q

Does the time taken for half life change?

A

No
The half life is fixed
Each time it halves it takes the same amount of time

38
Q

When you are given a graph about half life what must you do?

A

Draw on the lines to show the decay rates halving

39
Q

What is an example of radioactivity being used with Alpha particles?

A

Smoke alarms

40
Q

How do alpha particles help in smoke alarms?

A

Alpha particles are sent into a gap in the circuit
They ionise with the air allowing current to conduct
In a fire smoke absorbs the ions preventing current
This sounds the alarm

41
Q

What is an example of radioactivity being used with Beta particles?

A

Paper thickness control

42
Q

How do Beta particles help in paper thickness control?

A

Beta particles are passed through the paper with a sensor on the other side
If a lot of particles pass through the paper is too thin (rollers expand)
If too few particles pass through the paper is too thick (rollers contract)

43
Q

What is an example of radioactivity being used with gamma particles?

A

Leak detection in pipes

Radiotherapy

44
Q

How do Gamma particles help in leak detection in pipes?

A

A radioactive isotope is injected into the pipe
On the ground a Geiger counter will detect areas of high radioactivity
This is where the leaks are

45
Q

How do Gamma particles help in radiotherapy?

A

A controlled beam of gamma rays is used to kill cancer cells

It needs to be directed perfectly to avoid healthy cells

46
Q

What is an example of radioactivity being used with gamma particles or beta particles?

A

Radioactive tracers

47
Q

How do Beta or Gamma particles help in radioactive tracers?

A

A source is injected or swallowed by a patient
The progress of the tracer is monitored outside the body
Use a substance with a very short half life so the patient isn’t exposed for long

AQA GCSE - Physics (16 decks)

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