Radiation Flashcards
What is the plum pudding model?
Atoms are spheres of positive charge with tiny negative electrons stuck in them.
What was the result of Rutherford’s experiment?
A few particles were deflected straight back.
What did Rutherford’s experiment mean?
- Most of the mass of the atom is concentrated in centre as a tiny nucleus
- Nucleus must have large positive charge
- Most of atom is empty space
What do radioactive substances do?
Give out radiation from their nuclei.
Why is radioactive decay random?
- You can’t predict it
2. Unaffected by environmental conditions
Where does background radiation come from?
- Radon gas (51%)
- Rocks (14%)
- Food (12%)
- Medical X-rays (12%)
- Cosmic rays (10%)
- Nuclear industry (1%)
What are alpha particles?
Helium nuclei - 2 neutrons and 2 protons
What are beta particles?
Electrons
What are gamma rays?
Very short wavelength EM waves
What is the order of penetration?
Gamma > Beta > Alpha
What is the order of ionisation?
Alpha > Beta > Gamma
What charge do alpha particles have?
Positive
What charge do beta particles have?
Negative
What happens to alpha and beta particles when travelling through a magnetic or electric field?
Deflected in opposite directions.
What does radiation dose depend on?
Type and amount of radiation.
What occupations are at risk of radiation poisoning?
- Nuclear industry workers
- Radiographers
- Commercial pilots
- Underground miners
What half-life?
The average time taken for the number of nuclei in radioactive isotope sample to halve.
What radiation is used in smoke detectors and why?
Alpha, because smoke will absorb the radiation and stop the current - alarm sounds.
What radiation is used by tracers in medicine and why?
Short life beta or gamma, so the radiation can pass out of the body.
What radiation is used in radiotherapy?
Gamma, because they kill living cells and can treat cancer.
What radiation is used to sterilise food or surgical instruments?
Gamma, because it kills microbes.
What two types of damage can radiation cause living cells?
- Minor damage - cancer
2. Killing cells - radiation sickness
Why are beta and gamma sources more dangerous outside the body?
They can get to the delicate organs.
Why are alpha sources more dangerous inside the body?
They do their damage in a localised area.
What precautions can be taken when working with radioactive sources?
- Short time
- No skin contact
- Arm’s length, away from body
- Pointing away
What material is good at protecting against radiation?
Lead
