11. Nuclear Radiation Flashcards
What is a mass deficit?
The difference in mass of nucleus and mass of its constituents.
What is the nuclear binding energy?
The energy required to separate the nucleus into its constituents.
What us one atomic unit?
1/12th mass of carbon-12.
What is nuclear fission?
The splitting of a large nucleus into two daughter nuclei.
Why is energy released during fission?
Because the smaller nuclei have a higher binding energy per nucleon
What is nuclear fusion?
Where two smaller nuclei join together to form one larger nucleus.
Why is energy released during fusion?
The larger nucleus has a much higher binding energy per nucleon.
What conditions are needed for fusion?
High temperatures.
High density of matter (pressure)
What is the binding energy per nucleon?
Energy of a nucleus divided by the number of nucleons.
What can you deduce after plotting binding energy per nucleon by nucleon number?
Whether an element can undergo fission or fusion.
Which element undergo fission and fusion?
- Elements smaller than iron can undergo fusion.
- Elements bigger than iron can undergo fission.
Why are the conditions of fusion what they are?
High temp: as a large amount of energy is needed to overcome the electrostatic force of repulsion between nuclei.
High density of matte: so there is enough colliding protons undergoing fusion.
What must you do before taking readings for count rate?
Measure the background radiation, then subtract this from your measured values.
What are sources of background radiation?
- Radon gas.
- Artificial sources - caused by nuclear weapons testing and nuclear meltdowns.
- Cosmic rays.
- Rocks.
What is radiation?
- Where an unstable nucleus emits energy in the form of EM waves or subatomic particles.
- This is so they become more stable
What are the natures of the three types of radiation?
Alpha: an alpha particle (helium nuclei).
Beta: a fast-moving electron.
Gamma: An EM wave.
What are the ranges of the three types of radiation in air?
Alpha: 2- 10 cm
Beta: about 1m
Gamma: Infinite (follows inverse square law)
How ionising are the three types of radiation
Alpha: Highly
Beta: Weakly
Gamma: Very weakly
How absorbent are the three types of radiation?
Alpha: absorbed by paper.
Beta: absorbed by aluminium foil.
Gamma: absorbed by several meters of concrete OR several inches of lead.
Describe an experiment to differentiate between the different types of radiation?
- Using a Geiger-muller tube and counter find the background count when a radiation source is not present.
- Place the source of radiation close to the GM tube and measure the count rate.
- Place a sheet of paper between the GM tube and measure the count rate.
- If there is a considerable change then the source is emitting alpha.
- Repeat for aluminium foil and several inches of lead.
When does alpha decay occur?
Give a general equation.
In large nuclei, with too many protons and neutrons.
ⁿₚX → ⁿ⁻⁴ₚ₋₂Y + ⁴₂α
(nucleon number -4
proton number -2)
When does beta-minus decay occur?
Give a general equation.
In nuclei which are neutron-rich.
ⁿₚX → ⁿₚ₊₁Y + ⁰₋₁β + ᴠ̅ₑ
nucleon number +1
(ᴠ̅ₑ = electron nutrino)
What is the decay constant?
How is it calculated?
The probability of a nucleus decaying per unit time.
by finding the change in the number of nuclei (ΔN) of a sample over time (Δt), over the initial number of nuclei (N).
ΔN/Δt = -λN
What does the following formula show:
N = N₀e^(-λt)
The exponential decay of radioactive decay.
- N is the number of nuclei.
- N₀ is the initial number of nuclei.
- λ is the decay constant.
- t is the time passed.
What is a half-life?
The time taken for the number of nuclei to halve.
What is the activity of a radioactive sample?
The number of nuclei that decay per second.
When can the decay constant not be used?
When there is not a large number of nuclei in a sample
as the decay constant models the number of nuclei decayed by statistical means.
