Modern Physics Flashcards
Electron
An indivisible quantity of charge that orbits the nucleus of an atom.
Thermionic Emission
The emission of electrons from the surface of a hot metal.
Work Function
The minimum energy required to remove the loosest electrons from the surface of that metal.
X-rays
Electromagnetic radiation of extremely high frequency
Photoelectric Effect
The emission of electrons from the surface of a metal due to electromagnetic radiation of a suitable frequency hitting the metal.
Photon
A bundle of light energy.
Einstein’s Photoelectric Law
The energy of the fastest electron emitted is the difference between the energy of the photon and the work function of the metal.
Threshold Frequency
The minimum frequency needed to cause photoelectric emission.
Proton
Positively charged nucleons, with the same size of charge as the electron.
Neutrons
Electrically neutral nucleons.
Atomic Number
Number of protons in the nucelus of an atom.
Mass Number
Number of protons and neutrons in an atom.
Isotopes
Atoms with the same atomic number but different atomic masses.
Radioactivity
The spontaneous emission of radiation due to the natural disintegration of an unstable nucleus.
Radioation
The emission of particles of matter or photons of energy.
Ionisation
The charging of a neutral atom or molecule when it loses or gains one or more electrons.
Penetration
The distance the radiation travels through a medium.
Radioisotopes
An unstable isotope of an element that decays (disintegrates) spontaneously, emitting radiation.
Alpha emission
Emission of a helium nucleus from a large atom (4 2He)
Beta emission
The emission of an electron when a neurtron decays into a proton. (e-)
Gamma emission
The emission of high energy ohotons from an unstable nucleus.
Activity
The rate of emissions from that source. (Bq)
Half Life
Time taken for half the nuceli in a given sample to decay.
Law of Radioactive Decay
The acivity of a radioactive source is proportional to the nu,ber of undecayed nuclei present.
Fission
The splitting of a large nucleus into two smaller nuclei, of roughly equal mass, with emission of neutrons and release of energy.
Chain Reactions
Reactions where at least one neutron is released during each fission reaction.
Critical Mass
The minimum amount of fissile material needed in order for chain reactions to occur.
Fusion
Combining of two small nuceli to form a larger nucleus, with the release of energy.
Background radiation
Radiation coming from enviornmental sources such as Earth’s crust, the atmosphere and radioisotopes.
