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.
gold leaf electroscope
a device used to detect electric charge.
ground state
the lowest energy state of an atom.
hadron
particles and antiparticles that can interact through the strong interaction.
Intensity of radiation
At a surface is the radiation energy per second per unit area at normal incidence to the surface
Ion
A charged atom
Ionisation
Process of creating ions; when an atom/molecule loses or gains one or more electrons
Ionising radiation
Radiation that produces ions in the substance it passes through. It destroys cell membranes and damages vital molecules such as DNA directly or indirectly by creating free radical ions which reacts with vital molecules
Isotopes
Of an element or atoms which have the same number of protons in its nucleus but different numbers of neutrons
Kaon
A meson that consists of a strange quark or anti-quark and another quark or anti-quark
Lepton
Electrons, muons, neutrinos, and their antiparticles are classified as leptons because they cannot interact through the strong interaction. They interact through the weak interaction and, in the case of electrons and positrons, through the electromagnetic interaction
Lepton number
Electron number is assigned to every lepton and antilepton, On the basis that the total lepton number for each branch of the lepton family is always conserved
mass number
the number of protons and neutrons in a nucleus
matter waves
the wave-like behaviour of particles of matter
meson
a hadron consisting of a quark and an antiquark
Muon
A lepton which is negatively charged and has a greater rest mass than the electron
Neutrino
Uncharged lepton with a very low rest mass compared with the electron
Neutrino Types
There are 3 types of neutrinos: the electron neutrino, the muon neutrino, and the tau neutrino
Neutron
An uncharged particle that has a rest mass of 1.674*10^-27 kg. Neutrons are in every atomic nucleus except that of hydrogen
Nucleon
A neutron or a proton in the nucleus
Nucleon Number A
The number of neutrons and protons in a nucleus, also referred to as mass number
Nucleus
The relatively small part of an atom where all the atom’s positive charge and most of its mass is concentrated
Pair Production
When a gamma photon changes into a particle and an antiparticle
Photoelectric Effect
Emission of electrons from a metal surface when the surface is illuminated by a light of frequency greater than a minimum value known as the threshold frequency
Photon
Electromagnetic radiation consists of photons. Each photon is a wave packet of electromagnetic radiation. The energy of a photon is E = hf where h is Planck’s constant and f is the frequency of the radiation
Pion
A meson that consists of an up or down quark and an up or down antiquark
Positron
A particle of antimatter that is the antiparticle of the electron
Proton
a particle that has equal and opposite charge to an electron and has a rest mass 1.673 x10-27 kg which is about 1836 times that of an electron. Protons are in every atomic nucleus. The nucleus of hydrogen 1H1 is a single proton. The proton is the only stable baryon and has a quark structure of uud.
Quark
protons and neutrons and other hadrons consist of quarks. There are six types of quarks: the up quark, the down quark, the strange quark, the charmed quark, the top quark, and the bottom quark.
Quark model (or standard model)
a quark can join with an antiquark to form a meson or with two other quarks to form a baryon. An antiquark can join with two other antiquarks to form an anti baryon.
Rest energy
energy due to rest mass, m , equal to mc2, where c is the speed of light in free space
specific charge
charge/mass value of a charged particle
strangeness number
number assigned to every particle and antiparticle on the basis that strangeness is conserved in strong interactions, but not always in a weak reaction or decay
strong interaction
interaction between two hadrons
strong nuclear force
force that holds the nucleons together; attractive between 2 to 3 fm, repulsive below 0.5 fm
threshold frequency
minimum frequency of light that can cause the photoelectric emission for a given metal
Types of light spectra
Continuous spectrum - continuous range of colours corresponding to a continuous range of wavelengths
Line emission spectrum - characteristic coloured vertical lines, each corresponding to a certain wavelength
Line absorption spectrum - dark vertical lines against a continuous range of colours, each line corresponding to a certain wavelength.
Virtual photon
Carrier of the electromagnetic force; a photon exchanged between two charged particles when they interact.
W boson
Carrier of the weak nuclear force; W bosons have non-zero rest mass and may be positive or negative.
Wave-particle duality
- Matter particles have a wave-like nature, for example, electrons directed at a thin crystal are diffracted by the crystal, and particle-like behaviour, such as electrons in a beam deflected by a magnetic field. See de Broglie wavelength.
- Photons have a particle-like nature, as shown in the photoelectric effect, as well as a wave-like nature as shown in diffraction experiments.
Weak interaction
Interaction between two leptons.
Weak nuclear force
Force responsible for beta decay.
work function of a metal
mimimum amount of energy needed by an electron to escape from a metal surfacce
