Nuclear Physics Flashcards
What is an alpha particle?
2 protons and 2 neutrons
What is a beta particle?
High energy electron ejected from the nucleus
What is a gamma particle?
High energy electromagnetic radiation wave
What is nuclear fission?
Describe its process
- nucleus splits
- nucleus absorbs neutron
- nucleus splits into 2 smaller nuclei, 2/3 neutrons, gamma radiation and kinetic energy
- neutrons admitted absorbed by more nuclei triggering fission again (chain reaction)
Where does nuclear fission take place?
- energy released in a reactor (controlled)
- gamma rays and kinetic energy of fission absorbed by water, heating it
- steam produced generates electricity
-explosion in nuclear weapon caused by uncontrolled fission chain reaction
What are uses of radiation in medicine?
- radioactive tracers explore internal organs
- short half life so not in body for long
- gamma rays pass through body and are detected
What are uses of radiation in radiotherapy?
- gamma rays treat cancer
- carefully focused to kill cancer cells
- minimise damage to healthy tissues/cells
What is nuclear fusion?
What happens?
- 2 low mass nuclei join together to form a heavier nucleus
- some of the mass of the nuclei can be converted to energy which is released as radiation
- E = mc squared
What is background radiation?
Radiation present all around in the environment
What are natural sources of background radiation?
- radioactive rock
- cosmic rays from space
What are man made sources of background radiation?
- nuclear accidents
- fall out from weapons testing
What is carbon dating?
- half life or 5600 years
- measures age of ancient wood: other organic material
- measure count rate of radioactive carbon by compare to count rate of wood
What is uranium dating?
- half life of 4500 million years
- measure age of igneous rock
- decays to form atom of lead
- work out age of rock, compare to lead atoms
Give the 2 definitions of half life
1) time it takes for number of radioactive nuclei in a sample to halve
2) time taken for number of decays or activity to halve its initial level
What is irradiation
- exposing an object to nuclear radiation
-object does not become radioactive - only comes in contact with irradiation not isotope itself
What model of the atom did the alpha scattering experiment lead to by Neil Bohr and what did it state?
- nuclear model
- negative electrons orbit positive nucleus at fixed distances/shells
What was the alpha scattering experiment?
Why was gold used?
- alpha particles fired at a piece of thin gold foil
- gold can be hammered into a few atoms thick
What is the ionising power of?
1) alpha
2) beta
3) gamma
1) very strongly ionising
2) quite strongly ionising
3) weakly ionising
What is ionising radiation?
What are its risks?
-radiation that has enough energy to knock electrons off atoms so atoms become charged
-damage living tissue, mutate cells, cell death, increase likelihood of cancer
