Atoms & Nuclear Radiation (AQA GCSE Physics): Revision Notes
Contamination and irradiation
When dealing with radioactive materials, you can be exposed to radiation in two main ways. These are called irradiation and contamination. It's important to understand the difference between these two concepts for your exam.
What is irradiation?
Irradiation happens when you are exposed to radiation that comes from outside your body. The radiation source is not inside you or on you - it's separate from your body but sending out radiation towards you.
Key points about irradiation:
- The radiation travels through air or other materials to reach you
- You don't breathe in, eat, or drink the radioactive material
- When the radiation stops or you move away from the source, you are no longer being irradiated
- You don't become radioactive yourself
- The radiation can be gamma rays, beta particles, or X-rays
Example: Medical X-ray
Having an X-ray at the hospital is irradiation - the X-ray machine sends radiation towards your body, but you don't become radioactive. Once the X-ray is complete, you are no longer being exposed to radiation.
Alpha particles are different because they have a very short range in air (only about 5 cm). This means they are unlikely to cause harmful irradiation from outside the body as they can't travel far enough to reach you.
What is contamination?
Contamination is when radioactive material actually gets on your body or inside your body. This is different from irradiation because the radioactive source is now in direct contact with you.
There are two types of contamination:
External contamination
This happens when radioactive materials get onto your skin, hair, or clothing. The radioactive material is on the outside of your body.
Examples of External Contamination:
- Radioactive dust landing on your clothes
- Getting radioactive material on your hands
- Radioactive particles settling on your hair
Internal contamination
This occurs when radioactive material gets inside your body. You might breathe it in, eat it, or drink it.
Examples of Internal Contamination:
- Eating food that contains small amounts of radioactive materials
- Drinking water with radioactive substances in it
- Breathing in radioactive particles
Some everyday items like Brazil nuts, bananas, and certain drinks contain tiny amounts of natural radioactive materials. This is usually harmless because the levels are very low.
Key differences between irradiation and contamination
Irradiation:
- Radiation comes from outside your body
- You don't become radioactive
- Stops when you move away from the source
- The radioactive material stays separate from you
Contamination:
- Radioactive material is on or in your body
- Can continue to expose you to radiation even after you move away
- Material is in direct contact with your body
- Can enter through cuts in the skin, mouth, or nose
Critical Safety Distinction:
- With contamination, the radioactive source comes into contact with your skin or gets taken into your body
- With irradiation, the source does not come into contact with your skin
- Both can potentially cause damage to your cells
- Understanding the difference helps with proper safety procedures
Key Points to Remember:
- Irradiation = radiation from outside sources hitting your body
- Contamination = radioactive material on or inside your body
- You don't become radioactive from irradiation
- Contamination means direct contact with radioactive materials
- Both can be harmful but require different safety approaches