Unit E IB Physics terms

Nuclide

a different nucleus

Nucleon Number

A —> number of protons and neutrons in an atom

Proton Number

Z —> number of protons in the nucleus of an atom

Neutron number

number of neutrons in the nucleus of an atom

isotope

atom with the same atomic number but different mass

emission spectra

spectral lines which appear when energy is supplied to a gas at low temperature. Each lines corresponds to a certain energy level transition

absoprtion spectra

occurs when an electron in an atom of the absorbing material absorbs a photon. Energy of this photon must be identical to the difference between energy levels.

emission and absorption spectra

evidence for atomic energy levels

quantised energy and orbits

arise from the quantisation of anguar momentum in the Bohr model

work function

energy needed to do the work to overcome the attractive forces that act on the electron within the metal

threshold frequency

the minimum photon frequency below which no electron can be emitted

evidence of particle nature of light

photoelectric effect

another evidence of particle nature of light

compton scattering

unified atomic mass unit (u)

one/twelveth of the mass of a Carbon-12 atom

radioactive decay

the random and spontaneous process which the nucleus of an unstable atom change into a different nuclear configuration by emissions of alpha, beta particles or gamma radiation.

radioactive half-life

the rate at which the activity of a radioactive particle decreases to half its original amount.

mass defect

the difference between mass reagants and mass products which

binding energy

nergy released when a nuclide is assembled from its individual components (OR: energy required when nucleus is separated into its individual components)

binding energy per nucleon

energy released per nucleon when a nuclide is assembled from its individual components (OR: energy required per nucleon when nucleus is separated into its individual components)

activity

number of nuclear decay per second

background radiation

existing background count which is included in radioactive count

strong nuclear force

short range, attractive force between nucleons

decay constant

probabilty that an individual nucleus will decay over a certain period of time

evidence of nuclear energy levels

alpha and gamma decay

evidence or existence of the neutrino

beta decay

fission

process in which the heavy nucleus spilts into two daughter nuclei, releasing energy

heat exchanger

closed system in which energy is collected from reacotr to water

control rods

slows down/absorbs the neutrons in a nuclear reactor

moderators

nuclei in a nuclear reactor which slow down the neutrons by collisions

nuclear fusion

process in which two nuclei fuse to make a nucleus, a source of energy in stars

hydrostatic equilibrium

The state of a star when inward gravitational pressure balances the outward radiation pressure from the fusion reactions at its core.

lightyear

distance that light travels in a year in a vacuum

astronomical unit (AU)

distance from earth to sun

parsec

a unit of distance, measure by parallax method

star

Gravitationally bound mass of gas with fusion taking place at its core