Nuclear Radiation Flashcards
(27 cards)
What is the mass deficit/defect?
The difference between the total mass of a nucleus and the sum of the masses of its constituent nucleons
The total mass of a nucleus is less as some mass is converted into binding energy to hold the nucleus together
What is binding energy?
The energy required to break a nucleus into its constituent protons and neutrons
What can be said about nuclei with greater binding energy per nucleon?
Higher binding energy per nucleon indicates a higher stability
(Since more energy is required to pull the nucleus apart)
What does Eintein’s Theory of Relativity state about mass-energy equivalence?
Mass can be converted into energy and vice-versa
E = mc2
What is the Atomic Mass Unit u equal to?
The average mass of a nucleon, 1/12 the mass of a carbon-12 atom
1 u = 1.66 x 10-27 kg
1 u = 932.5 MeV
Which element has the highest binding energy per nucleon?
Iron, making it the most stable element
Thus, elements lighter than iron are likely to undergo fusion to become more stable
And elements heavier than iron are likely to undergo fission to become more stable
What is nuclear fusion?
When small nuclides combine together to make larger nuclei, releasing energy in the process
What are the conditions required for nuclear fusion?
Extremely high temperatures
So the nuclei have high Ek to overcome the electrostatic repulsion between protons
High densities
So the frequency of collisions between nuclei increase and heighten the likelihood of fusion reactions
What is background radiation?
Low levels of radiation from environmental sources, which are always present
What is radiation measured in?
Becquerel Bq
Which represents the radioactive decays/counts per second
What are some natural sources of background radiation?
Radon gas from rocks and soil
Rocks containing naturally occurring radioactive isotopes
Cosmic rays from space
Carbon-14 in biological materials
What are some man-made sources of background radiation?
Medical sources (e.g. X-rays, CT scans, radioactive traces, radiation therapy
Nuclear waste
Nuclear fallout from nuclear weapons (fallout is the residue radioactive material that is thrown into the air after a nuclear explosion
Nuclear accidents (e.g. Chernobyl)
What is the corrected count rate?
Corrected Count Rate = Total Count Rate - Background Count Rate
To find the corrected count rate, take readings with no radioactive source present and subtract this from the readings with the radioactive source present
How do Geiger-Muller (GM) tubes work?
When radiation enters the GM tube, it ionises the gas present in the tube
The ions conduct electricity, producing a pulse of current that is amplified and counted
What is radiation and the different types?
Radiation is the energy, in the form of EM waves or subatomic particles, that an unstable nucleus emits to become more stable
This includes:
Alpha particles α, Beta particles β and Gamma rays γ
What are alpha particles?
High energy particles made of 2 protons and 2 neutrons (the same as a helium nucleus)
Emitted from nuclei that are too large/heavy
What are beta particles?
High energy electrons (or positrons) emitted from the nucleus
Emitted by nuclei that have too many neutrons
What are gamma rays?
High energy electromagnetic waves
Emitted by nuclei with too much energy
What are the ionising qualities of the three different types of radioactive decay?
Alpha is the most/highly ionising
due to having the highest charge of +2e
Beta is moderately ionising
due to having a charge of ±2e
Gamma is the least/weakly ionising
due to having no charge
What are the penetrative qualities of the three different types of radioactive decay?
Alpha is the least/weakly penetrating
It has a range of a few cm in air and can be stopped by a sheet of paper
Beta is moderately penetrating
It can be stopped by a few mm of aluminium foil
Gamma is the most/highly penetrating
It has an infinite range and can be stopped by (a few cm of) lead or several metres of concrete
What is radioactive decay?
Radioactive decay is the spontaneous disintegration of a nucleus to form a more stable nucleus, resulting in the emission of alpha, beta or gamma
What is the nature of radioactive decay?
Spontaneous
It cannot be influenced by environmental factors
Random
The exact time of the decay of a nucleus cannot be predicted
How can the nature of a radioactive source be demonstrated?
By observing the count rate of a GM tube
When a GM tube is placed near a radioactive source, the counts are found to be irregular and unpredictable
When plotting the count rate against the time, there are fluctuations which provide evidence for the randomness of the radioactive decay
What is the decay constant?
The probability of a nucleus decaying per unit time
