6) Nuclear Physics Flashcards
(40 cards)
Why does an electric current through a filament wire cause the wire to emit electrons?
- current heats the wire.
- electrons gain sufficient k.e. to leave the filament.
When electrons are emitted from a filament wire, why do the filament wire and the metal plate be in an evacuated tube?
electrons would collide with gas atoms.
State what is meant by the binding energy of a nucleus.
energy needed to separate nucleus into constituent nucleons.
What is meant by the random nature of radioactive decay?
which atom decays at what time is chance.
Explain what is meant by radioactive half-life.
half-life is time for a number of nuclei to halve for a particular isotope.
Explain what is meant by radioactive decay constant.
λ is probability of decay in a unit time.
Give one reason why electromagnetic radiation is emitted following electron capture.
daughter atom might be excited and energy given up as electromagnetic radiation.
Explain what is meant by induced fission.
- a neutron strikes the nucleus.
- nucleus splits into two fragments.
State and explain one advantage of using nuclear fuel to produce electricity.
- less mass of fuel used.
- because more energy per kilogram.
State and explain one disadvantage of using nuclear fuel to produce electricity.
- hazardous waste.
- because fission products are radioactive.
State two physical features or properties required of the shielding to be placed around the reactor at a nuclear power station.
- thick.
- high density.
Which material is usually used for shielding in a nuclear reactor?
reinforced concrete.
Give three origins of the radiation that contributes to background radiation.
- cosmic rays.
- rocks.
- nuclear weapons testing.
Discuss the dangers of exposing the human body to a source of alpha radiation inside and outside the body.
- alpha radiation is highly ionising, hence damages cells.
- outside: less damage as absorbed by dead skin cells.
- inside: more damage as absorbed living tissue will absorb alpha radiation so can reach vital organs.
Suggest two reasons why an α particle causes more ionisation than a β particle of the same initial kinetic energy.
- α particle has much more mass/momentum than β particle.
- α particle travels much slower than a β particle.
Which ionizing radiation produces the greatest number of ion pairs per mm in air?
α particles.
Typical range in air of for α and β particles?
α 0.04
β 0.40
Following an accident, a room is contaminated with dust containing americium. Explain the most hazardous aspect of the presence of this dust to an unprotected human entering the room.
- dust may be ingested.
- causing cells to be made cancerous.
Explain the purpose of a moderator in a thermal nuclear reactor.
reduces the kinetic energy of neutrons so they are absorbed by the uranium fuel.
Explain why the shielding around the core become radioactive.
neutrons are absorbed by the nuclei in the shielding converting the atoms of the shielding into unstable isotopes.
Explain what is meant by a thermal neutron.
- slow moving neutrons
- they are in thermal equilibrium with the moderator.
Describe the changes made inside a nuclear reactor to reduce its power output and explain the process involved.
- insert control rods further into the nuclear reactor
- which will absorb more neutrons, reducing further fission reactions.
State the main source of the highly radioactive waste from a nuclear reactor.
fission fragments.
State the main interaction when an alpha particle is scattered by a gold nucleus.
electromagnetic.
