Particles & Radiation Flashcards
Alpha decay
Change in an unstable nucleus when it emits an alpha particle which is a particle consisting of two protons and two neutrons.
Alpha radiation
Particles that are each composed of two protons and two neutrons. An alpha particle is emitted by a heavy unstable nucleus which is then less unstable as a result. Alpha radiation is easily absorbed by paper, has a range in air of no more than a few centimetres and is more ionising than beta or gamma radiation.
Annihilation
When a particle and its antiparticle meet, they destroy each other and become radiation.
Antibaryon
A hadron consisting of 3 antiquarks
Antimatter
Antiparticles that each have the same rest mass and, if charged, have equal and opposite charge to the corresponding particle.
Antimuon
The antiparticle of the muon.
Antineutrino
The antiparticle of the neutrino.
Antinode
Fixed point in a stationary wave pattern where the amplitude is a maximum.
Antiparticle
There is an antiparticle for every type of particle. A particle and its corresponding antiparticle have equal rest mass and, if charged, equal and opposite charge.
Antiquark
Antiparticle of a quark.
Atomic mass unit (u)
Correctly referred to as the unified atomic mass constant; 1/12th of the mass of an atom of the carbon isotope 12C6, equal to 1.661x10^-27 kg.
Atomic number (Z)
…of an atom of an element is the number of protons in the nucleus of the atom. It is also the order number of the element in the Periodic Table.
Avogadro constant (Na)
The number of atoms in 12g of the carbon isotope 12C6. Na is used to define the mole. Its value is 6.02x10²³ mol⁻¹.
Baryon
A hadron consisting of three quarks.
Beta decay
Change in a nucleus when a neutron changes into a proton and an electron and an antineutrino are emitted if the nucleus is neutron-rich or a proton changes into a neutron and a positron and a neutrino are emitted if the nucleus is proton-rich.
Beta minus radiation. (B-)
Electrons (B⁻) emitted by and stable neutron rich nuclei (i.e. nuclei with a neutron/proton ratio greater than for stable nuclei). Beta minus radiation is stopped by about 5 mm of aluminium, has a range in air of up to a metre and is less ionising than alpha radiation and more ionising than gamma radiation
Beta plus radiation (B+)
Positrons (B⁺) emitted by unstable proton-rich nuclei (ie nuclei with a neutron/proton ratio smaller than for stable nuclei). Positrons emitted in solids or liquids travel no further than about 2mm before they are annihilated.
Conservation rules
Conservation of energy, charge, baryon number, and lepton numbers applies to all particle interactions. Conservation of strangeness applies to strong interactions only.
De Broglie wavelength
a particle of matter has a wave-like nature which means that it can behave as a wave. For example, electrons directed at a thin crystal are diffracted by the crystal. The De Broglie wavelength, λ, of a matter particle depends on its momentum, p, in accordance with De Broglie’s equation λ = h/p = h/mv, where h is the Planck constant.
de-excitation
process in which an atom loses energy by photon emission, as a result of an electron inside an atom moving from an outer shell to an inner shell or in which an excited nucleus emits a gamma photon.
electron
a lepton with rest mass 9.11x10⁻³¹ kg and electric charge -1.60x10e-19 C
electron capture
a proton-rich nucleus captures an inner-shell electron to cause a proton in the nucleus to change into a neutron. An electron neutrino is emitted by the nucleus. An X-Ray photon is subsequently emitted by the atom when the inner shell vacancy is filled.
electron volt
amount of energy equal to 1.6x10e-19 J defined as the work done when an electron is moved through a pd of 1V
energy levels
the energy of an electron in an electron shell of an atom or the allowed energies of a nucleus
excitation
process in which an atom absorbs energy without becoming ionized as a result of an electron inside an atom moving from an inner shell to an outer shell
excited state
an atom which is not in its ground state (i.e., its lowest ground energy state)
fluorescence
glow of light from a substance exposed to ultraviolet radiation; the atoms de-excite in stages and emit visible photons in the process
gamma radiation
electromagnetic radiation emitted by an unstable nucleus when it becomes more stable. See pair production.