8.1 Radioactivity Flashcards
Describe the Rutherford scattering experiment set up.
- Beam of alpha particles directed at thin gold foil
- In vacuum so that no collisions with air particles occured
- Movable detector would observe scattering angle
What were the observations of the Rutherford scattering experiment?
- Most alpha particles passed through the gold foil
- Some alpha particles were deflected by large angles
- A few alpha particles were reflected back
What were the conclusions of the Rutherford scattering experiment?
- An atom is mostly empty space and the nucleus is small
- The nucleus is positively charged
- The nucleus is very dense
What are the three types of radiation?
- Alpha
- Beta
- Gamma
What is an alpha particle?
2 protons and 2 neutrons
(aka a Helium nucleus)
What is a beta particle?
Electron
(or a positron)
What is a gamma particle?
Very high energy photon
(aka gamma ray)
Rank radiation from most ionising to least.
- Alpha
- Beta
- Gamma
Rank radiation from fastest to slowest
- Gamma
- Beta
- Alpha
Rank radiation from most penetrating to least.
- Gamma
- Beta
- Alpha
What are the charges of the three types of radiation?
- Alpha is +2e
- Beta is -e (or +e)
- Gamma is 0
Which types of radiation are effected by magnetic fields?
Alphs and beta
What type of radiation can be stopped by a few centimeters of air or paper?
Alpha
What type of radiation can be stopped by a few millimeters of aluminium?
Beta
(and by extension, alpha)
What type of radiation can be stopped by a few centimeters of lead or a few meters of concrete?
Gamma
(and by extension alpha and beta)
What type of radiation follows the inverse square law?
Gamma
What does the inverse square law state?
Intentisty is inverse;y proportional to the square of the distance from the source.
What are some safety procedures that need to be followed?
- Never directly handle sources
- Use long-armed tong to increase distance from source
- Display signage warning others sources are in use
- Keep time source is being used to a minimum
- Store sources in lead boxes when not in use
What are some sources of background radiation?
- Radon gas
- Rocks
- Comic rays
- Nuclear weapons testing
- Nuclear disasters
How is corrected count calculated?
Corrected count = Total count - Background count
What does it mean for radioactive decay to be random in nature?
Which nucleus will decay and when is unpredictable and determined by chance.
Define decay constant.
The porbability of a nucleus decaying per second.
What is the equation for rate of change of nuclei number?
What do the letters represent in this equation?