Flashcards
Nuclear Physics
Flashcards do conjunto (31)
- 1What do radioactive substances contain?contain unstable nuclei that become stable by radioactive decay
- 2What happens during radioactive decay?radioactive substances emit radiation and turn into other elements
it is a random process (can't be predicted) and isn't affected by external conditions - 3What is background radiation?-around us all the time
-radiation from radioactive substances in the environment, space & from devices (e.g. X-ray tubes) - 4Plum pudding modelatoms were thought to consist of spheres of positive charge with electrons stuck into them
- 5What was the alpha particle scattering experiment?alpha particles fired at thin gold foil
- 6Why did most of the alpha particles pass straight through the foil?most of the atom is empty space
- 7Why were some of the particles deflected through small angles?the nucleus has a positive charge
- 8Why did a few rebound through very large angles?nucleus has a large mass & a very large positive charge
- 9Alpha decayChange in nucleus: loses 2p and 2n
Particle emitted: 2p and 2n - 10Beta decayChange in nucleus: neutron becomes proton & electron
Particle emitted: electron instantly emitted - 11Alpha particlewhen emitted, atomic no. goes down by 2 & mass no. goes down by 4
- 12Beta particleproton stays in nucleus so atomic no. goes up by 1, mass no. is unchanged (electron instantly emitted)
- 13Gamma radiationno change in atomic number/mass number as gamma ray is electromagnetic wave released from nucleus; no charge or mass
- 14What is ionisation?when nuclear radiation travels through a material it will collide with atoms of the material; can damage or kill a living cell
- 15Features of an alpha particle-relatively large so lots of collisions (strongly ionising)
-don't penetrate far into a material
-can be stopped by paper, skin or a few cm of air
-deflected by electric/magnetic fields - 16Features of a beta particle-smaller & faster so less ionising
-penetrate further
-blocked by a few m of air or aluminium
-deflected by electric/magnetic fields in opposite direction to alpha - 17Features of a gamma ray-electromagnetic so travel a long way thru material before colliding
-weakly ionising & very penetrating
-cm of lead or m of concrete needed to absorb most of radiation
-not deflected by electric/magnetic fields - 18Half-lifethe average time it takes for the number of unstable nuclei in a radioactive isotope in a sample to halve
- 19What is the 'activity' of a radioactive source?the number of nuclei that decay per second
- 20Use of alpha sourcesmoke alarms:
-particles not dangerous as poorly penetrating
-needs a half-life of several years - 21Use of beta sourcesthickness monitoring in manufacture of paper/foil:
-alpha would by stopped by thin paper & gamma would pass thru it
-needs half-life of many years so decreases in count rate are due to thickness change - 22Use of gamma and beta sourcestracers in medicine:
-source is swallowed/injected by patient
-progress around body is monitored by external detector
-needs half-life of a few hours so patient not exposed to unnecessary radiation - 23Radioactive datingcarbon dating: finds age of wood & other organic materials
uranium dating: fins age of igneous rocks - 24What is nuclear fission?the splitting of a nucleus into two approximately equal fragments and the release of 2 or 3 neutrons
- 25How does fission occur?Uranium-235 or plutonium-239 nucleus must absorb a neutron then the nucleus splits into 2 smaller nuclei
- 26What are control rods in a nuclear reactor used for?absorb fission neutrons to ensure that on average, only one neutron per fission goes on to produce further fission
- 27What is a chain reaction?occurs when neutrons from the fission go on to cause other fission events
- 28What is nuclear fusion?the process of forcing 2 nuclei close enough together that they form a single larger nucleus
- 29What is the problem with producing energy from nuclear fusion?nuclei approaching each other will repel each other as they both have positive charge
- 30How is this issue solved?nuclei must be heated to high temp. to give them enough energy to overcome repulsion and fuse
- 31Why can't the reaction take place in a normal container?because of the high temperatures needed
have to be contained in a magnetic field
Informações
- Descrição
- GCSE Physics (2) Additional) FlashCards sobre Nuclear Physics, criado por Alex C em 16-06-2016.
- Criado por
- Alex C · jun 2016
- Atualizado
- 17 jun 2016
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