What does an Alpha particle consist of?
2 Protons and 2 Neutrons
The same as a helium nucleus
What does a Beta particle consist of?
High Speed Electron from nucleus
What is Gamma radiation?
Electromagnetic wave with high frequency
What is the range and penetration power of the different types of radiation?
- Alpha – stopped by paper – range in air of up to 10 cm
- Beta – stopped by few mm of aluminium – range in air 1m
- Gamma - stopped by several cm of lead – unlimited range in air
Name 2 ways radiation can be detected.
Radiation can be detected using:
• Photographic film
• Geiger-Muller detector
What is the definition of Half Life?
• The time it takes for the number of radioactive nuclei in a sample to halve
Or
• The time it takes for the activity (count rate) from a sample to halve
What is background radiation?
Radiation that is around us all the time.
• Mostly from natural sources e.g. Radon gas, rocks, food and drink, cosmic rays.
• Some comes from artificial sources e.g. X-rays and Nuclear Power
What is an Isotope?
Atoms of the same element with:
• The same number of protons (and electrons)
• A different number of neutrons
What happens to the nucleus that emits and alpha particle?
When an alpha particle is released, the atom looses 2 protons and 2 neutrons. The atomic no. goes down 2 and the mass goes down 4.
What happens to the nucleus that emits a beta particle?
When a beta particle (electron) is released a neutron changes into a proton so the atomic number goes up 1 and mass stays the same.
What happens to a nucleus that emits gamma radiation?
When gamma radiation is released the atom looses energy in the form of gamma radiation.
The element does not change because the number of protons remains constant.
What is activity?
The activity of a sample is the number of radioactive atoms decaying per second.
It is measured in Becquerel’s (Bq).
NB Radioactive decay is random. It is not possible to predict exactly when an individual nucleus will decay but given a large number of them you can predict roughly how many will decay per second.
What are the dangers of radioactivity?
- radiation can cause mutations in living organisms
* radiation can damage cells and tissue
What precautions must be taken when handling radioactivity?
- Use Tongs
- Keep source at arm’s length away from eyes
- Store source in lead lined box in a locked cupboard
- Lead screens are used to protect people or areas of the body that do not need to be exposed.
- People who work with radiation often wear a badge which monitors radiation dose
What is Ionisation?
- An ion is a charged atom
- When radiation collides with atoms it can knock electrons from their structure causing the atom to become charged.
- Alpha radiation is most ionising
- Gamma is least ionising.
How is radiation affected by electric and magnetic fields?
Alpha and Beta radiation is deflected in different directions. Gamma radiation is not deflected.
In an electric field beta is negatively charged and is attracted towards the positive plate. Alpha is positive and so it is deflected towards the negative plate.
In a magnetic field the direction of deflection can be worked out using Flemings Left Hand Rule.
What is a nucleon?
A particle in the nucleus (either a proton or a neutron).
