P2 - Radioactivity
저자: A Jenkins
1. How long does a radioactive material last?
1.1. Decays over time
1.2. half-life is time for half the atoms to decay
1.3. half-lives are different for different materials
2. Uses (7)
2.1. radioactive tracers
2.2. carbon dating
2.3. thickness monitoring
2.4. cancer treatment
2.5. checking welds
2.6. sterilising food and medical equipment
2.7. smoke alarms
3. Types
3.1. Alpha
3.1.1. Helium nucleus: two protons, two neutrons
3.1.2. stopped by few cm air, sheet of paper
3.1.3. highly ionising
3.1.4. most dangerous inside the body
3.2. Beta
3.2.1. fast moving electrons
3.2.2. stopped by few mm of aluminium
3.3. Gamma
3.3.1. high energy electromagnetic wave
3.3.2. very penetrating
3.3.3. most dangerous outside the body
4. Where does it come from?
4.1. unstable atomic nucleus
4.1.1. (HIGHER: imbalance of protons and neutrons)
4.2. background radiation
4.2.1. all around us, all the time
4.2.2. natural sources (most)
4.2.2.1. cosmic rays
4.2.2.2. rocks and soil
4.2.2.2.1. radon gas
4.2.2.3. food and drink
4.2.3. manmade sources
4.2.3.1. medical uses
5. Dangers
5.1. All are dangerous
5.2. Can cause cancer
5.3. Disposal causes problems
5.3.1. needs to be stored for 1000s of years