What is radioactivity?
Emission of ionising radiation from an unstable nucleus.
What are the three most common types of radiation?
Alpha, beta minus, and gamma rays.
How can radioactivity be detected?
Using a Geiger muller tube and scaler counter
What is the usual unit for count rate?
Becquerels. Bq
What are sources of background radiation?
Cosmic rays, radioactive elements in rocks of Earth’s crust occur naturally.
Nuclear waste and fallout from testing bombs is due to humans
What will background radiation result in when measuring activity of samples?
Increased measure of activity by the same amount and therefore a systematic error.
How to account for background radiation when measuring count rate?
Measure background count rate for 5 minutes with no source present and subtract count rate from future experiments.
What can be changed to make a more suitable container apart from changing the thickness of an absorber?
Use a different type of absorber.
What is the range of alpha particles in air?
A few cm (5-10).
What is the range of beta particles in air?
A few meters.
What is the range of gamma radiation in air?
A few kilometres.
What can alpha particles be absorbed/blocked by?
Paper or skin.
What can beta particles be absorbed/blocked by?
A few mm of aluminium.
What can gamma radiation be absorbed/blocked by?
A few cm of lead or a few m of concrete.
Why do radioactive particles have limited range?
They lose energy by ionising atoms in their path as they pass through a material or medium.
Why do alpha particles have the shortest range?
Large size and charge, therefore cause a lot of ionisation and lose energy quickly.
Why does gamma radiation have a very long range?
No charge, negligible size, high energy, and low ionising power - loses energy very slowly as it passes through matter.
What is the nucleus left after decay has taken place?
Daughter.
When is gamma radiation emitted?
Emitted along with alpha or beta particles to remove excess energy if daughter nucleus in excited state
What does spontaneous mean?
Not affected by ANY external factors such as pressure, temperature, or chemical reactions.
What does random mean?
Cannot predict when a certain nucleus will decay or which nuclei will decay in a given time.
What does A mean in the decay equation?
Activity. Number of nuclei decaying per unit time.
What is half life
Average time taken for activity to reach half the initial value
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Practical Skills Y137
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Module 4 Basic Wave Properties / Refraction49
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Module 4 EM Spectrum, diffraction, polarisation24
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Module 4 Interference23
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Module 4 Standing Waves28
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Module 4 Wave Particle Duality18
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Module 4 Photoelectric effect25
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Module 4 Fundamental electricity41
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Module 4 Series and Parallel Circuits20
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Module 4 Potential Dividers22
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Module 4 Resistance Characteristics15
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Module 4 EMF and Internal Resistance21
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Module 4 Resistivity13
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Module 3 Motion46
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Module 3 Projectiles21
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Module 3 Dynamics26
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Module 3 Statics17
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Module 3 Moments16
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Module 3 Pressure Density Archimedes16
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Module 3 Work Energy Power23
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Module 3 Newton's Laws and Momentum23
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Module 3 Springs & Hooke's law30
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Module 3 Stress, Strain, Young Modulus28
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Module 5 Simple Harmonic Motion38
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Module 5 Circular Motion19
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Module 5 Gravitational Fields39
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Module 5 Life of Stars62
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Module 5 Cosmology61
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Module 5 Specific Heat Capacity36
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Module 5 Ideal gases18
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Module 5 Kinetic Theory28
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Module 6 Capacitors39
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Module 6 Electric Fields32
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Module 6 Magnetic Fields34
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Module 6 Electromagnetism35
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Module 6 Nuclear and Particle Physics61
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Module 6 Radioactivity42
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Module 6 Fission and Fusion54
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Module 6 Medical Imaging72
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Module 6 X-rays54
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Revision - Exploring Physics definitions85
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Revision - Modelling Physics definitions103
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Module 6 Medical Imaging COPY72
