P4 Flashcards
Radioactive Decay
Some atomic nuclei are unstable. The nucleus gives out radiation
as it changes to become more stable
What is the activity?
Activity is the rate at which a source of unstable nuclei decays
What is activity measured in?
Becquerel (Bq)
What is the Count - Rate?
The number of decays recorded each second by a
detector (eg Geiger-Muller tube)
How can nuclear radiation be emitted?
- Alpha Particle
- Beta Particle
- Gamma Ray
What does an Alpha Particle consist of?
Consists of two neutrons and two protons, it is the same as a helium nucleus
What does a Beta Particle consist of?
Electron
What is a Gamma Ray?
Electromagnetic radiation
What is the air range of a Beta Particle?
1 metre
What is the air range of a Gamma Ray?
Hundreds of metres
What is the air range of an Alpha Particle?
8 centimetres
What is an Alpha particle stopped by?
Skin or Paper
What is a Gamma-ray stopped by?
Thick Lead
What is a Beta particle stopped by?
Thin Aluminium
How many atoms can 1 Alpha Particle Ionise?
10,000; it has a high charge, cant travel far
How many atoms can 1 Gamma Ray Ionise?
1; has no charge, can travel far
How many atoms can 1 Beta Particle Ionise?
100; small charge, can travel little distance
If there are too many neutrons, what radiation would we use?
Beta Particles; neutron splits into a proton and neutron, the electron is emitted (beta), which will carry a lot of energy
Ionisation
Radiation removes electrons from atoms, turning them into ions
What is the most dangerous Particle to ingest?
Alpha
- Ionising
- Can’t leave the body (least penetrating)
What can radiation be used for?
- Sterilising medical equipment (gamma)
- Irradiation (gamma)
- Medical Tracers (Beta/Gamma)
- Smoke Detector (Alpha)
- Measure paper Thickness (Beta)
What is the most accurate way to measure the speed of Decay?
Half Life
What is Half-Life?
The time it takes for the number of nuclei of the isotope in a sample to halve, or the time it takes for the count rate (or activity) from a sample containing the isotope to fall to half its initial level.
What is Irradiation?
Irradiation is the process of exposing an object to nuclear radiation
Radioactive Contamination?
Radioactive contamination is the unwanted presence of materials containing radioactive atoms in other materials
Preventions of Contamination?
- Tongs
- Stored in Lead Lined Containers
- Protective Clothing
- Direct Sample Away
- Limit Time of Use
Factors affecting how dangerous a radioactive sample is?
- Type of radiation
- Its Half-Life
- Length of Time exposed to it
A sample of C-14 has a count rate of 80 and a Half-Life of 2 days. How long will it take before the count rate is 10?
6 Days
What does absorbing electromagnetic radiation do?
Makes electrons move away from the nucleus to a higher energy level
What does emitting electromagnetic radiation do?
Makes electrons move closer to the nucleus to a lower energy level
What is an isotope?
An element with the same number of protons but a different number of neutrons
Why are some atomic nuclei unstable?
If there are too many or too few neutrons
When does beta decay occur?
When there are too many neutrons
When does Alpha decay occur?
When there are not enough neutrons
When will Gamma radiation occur?
After Beta/Alpha radiation, the nucleus is full of energy making it very hot, it will loose energy by emitting a gamma ray
What dictates how far it can travel through the air?
How ionising it is; if it’s highly ionising it will run out of energy quickly, else, if its poorly ionising they can travel farther before running out of energy
How can radiation be damaging?
It can change the way that cells behave and also destroy/damage cells
Pros and cons of radiation?
- Can cause damage to living cells but only slightly
- Can preserve foods
