Modern Physics Flashcards
Electron
A subatomic particle which orbits the nucleus full stop has a charge of e which is the fundamental quantity of charge
Thermonic emissiom
The release of electrons from the surface of a hot metal
Work function
The minimum energy required by a photon to remove the losses electron from the surface of a metal
X Rays
Electromagnetic radiation of extremely high frequency, short wavelength which are produced when high speed electrons strike a heavy metal target
Photoelectric effect
The release of electrons from the surface of a metal due to electromagnetic radiation of a suitable frequency hitting is
Photon
A discrete packet of electromagnetic energy. Its energy depends on its frequency
E = hf
Threshold frequency
The minimum frequency needed for photoelectric emission
Protons
Positively charged nucleons with the same size charge as the electron
Neutrons
Electrically neutral nucleons, they have slightly more mass than protons
Atomic Number
The number of protons in the nucleus of an atom
Mass number
The total number of protons and neutrons in the nucleus of an atom
Isotopes
Ashams which have the same atomic number but different atomic mass
Radioactivity
The spontaneous emission of radiation due to the natural disintegration of an unstable nucleus
Ionisation
The charging of a neutral atom or molecule when it loses or gains water more electrons
Penetration
The distance the radiation travels through a medium
Radioisotope
An unstable isotope of an element that the case spontaneously, emitting radiation
Alpha radiation
The emission of a helium nucleus from a large atom
Beta radiation
The emission of an electron when a neutron decays into a proton
Gamma radiation
The emission of high energy photons from an unstable nucleus
Activity
The number of nuclei in a radioactive sample decaying per second
1 Becquerel
Units of activity equaling 1 disintegration per second
Law of radioactive decay
The activity of a sample is directly proportional to the amount of present
A=-λN
Half life
The time taken for half of the atoms present in a radioactive sample to decay
T= ln2/λ
Nuclear fission
The splitting of a large nucleus into two smaller nuclei, of roughly equal mass, with emission of neutrons and release of energy
Nuclear fusion
The joining up of two smarter nuclei to form a larger nucleus with release of energy
Chain reactions
Reactions were at least one neutron is released during each fission reaction
1 electronvolt
The energy gained or Lost by an electron when it moves through potential difference of 1 V
Critical mass
The minimum amount of the fissile material needed in order for chain reactions to occur
Radiation
The emission of particles of matter or photons of energy
Background radiation
Radiation that comes from environmental sources including the Earth’s crust, the atmosphere, cosmic rays and radioisotopes
