Particles and nuclides (1) Flashcards Preview

Physics A-Level AQA definitions > Particles and nuclides (1) > Flashcards

Flashcards in Particles and nuclides (1) Deck (36)
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1
Q

Atoms

A

made up of a very small central nucleus containing protons and neutrons, surrounded by orbiting electrons. They are electrically neutral overall, meaning they have the same number of protons and electrons.

2
Q

Proton (atomic) number

A

number of protons contained in the nucleus.

3
Q

Nucleon (mass) number

A

total number of protons and neutrons contained in the nucleus.

4
Q

Protons

A

positively charged particles with a relative charge of +1. Relative mass 1.

5
Q

Electrons

A

negatively charged particles with a relative charge of -1. Relative mass 1/1800.

6
Q

Neutrons

A

electrically neutral particles with a relative charge of 0. Relative mass 1.

7
Q

Ions

A

an atom which has lost or gained electrons (excess electrons = negatively charged ion, shortage of electrons = positively charged ion).

8
Q

Relative atomic mass

A

the RAM of an element compares the mass of atoms of the element with the carbon-12 isotope.

9
Q

Nucleon

A

the word used to describe protons or neutrons. These are particles that exist in the nucleus.

10
Q

Isotopes

A

nuclei with the same number of protons, but different numbers of neutrons.

11
Q

The strong nuclear force

A

one of the four fundamental forces of nature (including electromagnetic, weak and gravitational forces). It is a very short-range force and acts between nucleons (protons and neutrons) holding nuclei together.

12
Q

Neutrino, ν

A

a neutral, almost massless fundamental sub-atomic particle that rarely interacts with matter. There are three forms of the neutrino: the electron-neutrino, νe; the muon-neutrino, νµ; and the tau-neutrino, ντ.

13
Q

Antineutrinos

A

the antiparticles of the neutrino.

14
Q

Rest-mass energy

A

the amount of energy released by converting all of the mass of a particles at rest into energy using Einstein’s famous mass-energy equation, E=mc^2, where m is the rest mass of the particle and c is the speed of light.

15
Q

Mega electron-volts

A

the energy of nuclear particles is usually given in MeV, mega electron-volts. One electron-volt is a very small amount of energy, equivalent to 1.6×〖10〗^(-19)J. This is the same numerical value as the charge on an electron and is defined as the amount of energy needed to accelerate an electron of charge ‘e’, (1.6×〖10〗^(-19)C) through a potential difference of 1 volt. One MeV is a million electron-volts, equivalent to 1.6×〖10〗^(-13)J. This unit comes from the definition of the volt. A volt is the amount of energy per unit charge so energy = charge x volts.

16
Q

Annihilation

A

when a particle meets its antiparticle and their total mass is converted to energy in the form of two gamma ray photons, the particles annihilate each other.

17
Q

Antiparticles

A

fundamental particles with the same mass and energy as their particle counterparts, but have opposite properties such as charge. When a particle meets its antiparticle they annihilate, converting to gamma ray photons.

18
Q

Quarks

A

fundamental particles that make up particles such as protons and neutrons. They exert the strong nuclear force on one another.

19
Q

Gluons

A

one of the four exchange particles of the Standard Model. Gluons act between quarks holding them together. Gluons have an extremely short range of action of about 〖10〗^(-15)m.

20
Q

Deep-inelastic scattering

A

involves firing electrons at protons at very high energies (hence the word ‘deep’). Elastic scattering, for example, involves two particles such as two protons colliding with each other and rebounding off each other with the same kinetic energy – rather like two snooker balls hitting each other head-on and rebounding back. The word ‘elastic’ in this context means that no kinetic energy is lost. Inelastic scattering involves the conversion of kinetic energy into other forms. In this case the electrons penetrate into the proton and interact with the quarks (via exchange of photons); kinetic energy is converted into mass as the proton shatters, producing a shower of other particles. Using the snooker analogy, it would be as if one snooker ball entered the second ball causing it to break into other pieces as the first snooker ball scattered away from it.

21
Q

Exchange particles

A

particles involved with the interaction of particles via the four fundamental forces of nature on the quantum scale. Exchange particles are only created, emitted, absorbed and destroyed between the interacting particles.

22
Q

Macroscopic

A

means ‘large-scale’, as opposed to microscopic, quantum scale. Quantum effects operate at distances less than about 100nm, so anything above this scale is considered macroscopic, and classical (sometimes Newtonian) physics is applied.

23
Q

Feynman diagrams

A

used to represent reactions or interactions in terms of particles going in and out, and exchange particles.

24
Q

Particle lifetime

A

the average time that a particle exists from its creation to its decay.

25
Q

Mesons

A

hadron particles made up of a quark-antiquark pair.

26
Q

Virtual photon

A

the exchange particle for the electromagnetic interaction.

27
Q

Hadrons

A

particles subject to the strong interaction. There are two classes of hadrons:
• baryons (proton, neutron) and antibaryons (antiproton and antineutron)
• mesons (pion, kaon)

28
Q

Baryon number, B

A

a quantum number that describes baryons. Baryons have B = +1; antibaryons, B = -1; non-baryons, B = 0. Baryon number is always conserved in particle interactions.

29
Q

Free neutrons

A

are unstable and decay via the weak interaction forming a proton, β- particles and an electron neutrino.

30
Q

Pion

A

the exchange particle of the strong nuclear force between baryons.

31
Q

Kaon

A

a particle that can decay into pions.

32
Q

Leptons

A

particles that are subject to the weak interaction. Include electron, muon, neutrino (electron and muon types) and their antiparticles.

33
Q

Lepton number, L

A

a quantum number used to describe leptons. Leptons have L = +1; antileptons, L = -1; non-leptons, L = 0. Lepton number is always conserved in particle interactions.

34
Q

Muon

A

a particle that decays into electrons.

35
Q

Strange particles

A

particles that are produced through the strong interaction and decay through the weak interaction (e.g. kaons).

36
Q

Strangeness, S

A

a quantum number to describe strange particles. Strange particles are always created in pairs by the strong interaction (to conserve strangeness). In weak interactions, the strangeness can change by -1, 0 or +1.