P7 Radioactivity Flashcards
What is the identity of (α)?
A helium nuclei
What is identity of (β)?
Electrons
What is the identity of (γ) ?
Electromagnetic radiation
What is (α) stopped by?
Paper
What is (β) stopped by?
1mm of aluminium
What is (γ) stopped by?
Thick lead
Range in air of (α)
About 5cm
Range in air of β
About 1m
Range in air of (γ)
Unlimited
Relative ionisation of different types of radiation
α=very stong
β=strong
γ=weak
What is meant by the activity of a radioactive source?
number of unstable atoms that decay per second (or rate of decay of unstable atoms in source)
Explain why most alpha particles can pass through metal foil?
nucleus very small compared to atom
so most alpha particles don’t pass near enough to nucleus to be affected by it
Explain what is meant by a nuclear chain reaction?
a sequence of induced fission events in which each event causes further fission events which in turn cause further fission events,
each fission occurs when nucleus of a fissionable atom absorbs a neutron and splits into two smaller fragment nuclei,
releasing several neutrons which can cause other fissionable nuclei to split
Explain what would happen in a nuclear reactor is coolant fluid leaked out of the core?
reactor core overheats,
as energy still released from fuel rods
Explain what would happen in a nuclear reactor if control rods were pushed further into the reactor core
control rods absorb more neutrons,
so number of fission events/second decreases,
so rate energy is released from fuel rods decreases
What is meant by nuclear fusion?
process in which two small nuclei fuse to form a single larger nucleus, releasing energy
Explain why 2 nuclei repel each other when they get close
any particles with same type of charge repel each other all nuclei positively charged,
so when two nuclei approach they repel each other
Explain why they need to collide at high speed in order to fuse together
when two nuclei collide they only fuse together if sufficient Kinetic Energy to overcome force of repulsion between them,
so must collide at high speed to fuse
Give 3 reasons why nuclear fusion is difficult to acheive in a reactor?
plasma containing nuclei to be fused at very high temperature so nuclei move fast enough to fuse,
plasma difficult to control at such high temperatures,
strong magnetic fields prevent plasma touching inside walls of container and losing internal energy
What is a half life?
The amount of time taken for the amount of radiation emitted by a source by a half
What is activity measured in?
Becquerels (Bq)
