Particles and Waves Flashcards
Absolute refractive index
the absolute refractive index (or more simply, the refractive index), n, of a medium is the ratio sinθ1/sinθ2
where θ1 is in a vacuum, and θ2 is in the medium
Angle of incidence
the angle between the incident ray and the normal
Angle of refraction
the angle between the refracted ray and the normal
Atomic mass units (u)
by definition one twelfth of the mass of a carbon-12 nucleus
Atomic number
the number of protons in an atomic nucleus. It is this number that determines the element
Binding energy
the energy needed to split a nucleus into its separate nucleons
Chain reaction
when a nucleus undergoes fission it releases neutrons that can go on to collide with other nuclei, causing further fission reactions. If there is a sufficient concentration of suitable nuclei, the process becomes self-sustaining.
Coherent waves
coherent waves are waves that have the same frequency, speed and have a constant phase relationship
coherent waves are waves that have the same frequency, speed and have a constant phase relationship
part of a spectrometer that is used to produce a parallel beam of light
Critical angle
the maximum value of the angle between the normal and the ray in glass, θ glass, for which refraction can occur
Diffraction
an effect that causes waves to bend as they go past the end of an obstacle or through a small gap in a barrier
Dispersion
the process of splitting up light into its constituent colours
Electromagnetic waves
the spectrum of waves that includes radio, visible light, X-rays etc
Excited state
any atomic energy level higher than the ground state
Fission
the splitting of a large atomic nucleus into smaller fragments, with the resultant release of excess energy
Frequency
the number of complete cycles of a wave passing a given point in a given time, usually per second. Frequency is measured in hertz (Hz) where 1 Hz = 1 wave per second.
Fundamental unit of charge
e; the magnitude of charge carried by one electron or one proton. Equal to 1.60 x 10-19 coulombs
Grating
a transparent slide of glass or plastic that has a very large number of equally-spaced grooves machined on to its surface. Each groove acts as a source for coherent beams of light.
Ground state
the lowest energy level of an atom
Induced fission
the deliberate splitting of a large nucleus caused by the collision of the nucleus with a neutron
Ionisation level
the energy level at which an electron can break free from an atom
Irradiance
the power per unit area of radiation incident on a surface
Isotopes
different forms of the same element. The isotopes of an element contain the same number of protons but have different numbers of neutrons.
Line absorption spectrum
a spectrum that consists of narrow dark lines across an otherwise continuous spectrum
Line emission spectrum
a spectrum consisting of narrow lines of light, the position of which depend on the substances producing the light
Magnetic field
a magnetic field is a region in which a moving charge experiences a magnetic force
Mass defect
the difference between the mass of a nucleus and the total mass of an equal number of individual nucleons
Mass number
the total number of nucleons in the nucleus of an atom
Monochromatic
radiation consisting of a single frequency
Monochromatic light
light of one wavelength (and therefore one colour)
Normal
a line drawn at right angles to a surface or the boundary between two different media
Nucleon
the general term for protons and neutrons
Nuclide
the nuclei of one particular isotope. These nuclei all have the same atomic number and mass number.
Path difference
the difference in path lengths of two sets of waves
Period
the time to make one complete wave. Period is measured in seconds.
Photocathode
the terminal from which electrons will be emitted due to the photoelectric effect
Photoelectric effect
the emission of electrons from a metal due to the effect of electromagnetic radiation
Photoelectrons
free electrons produced by the photoelectric effect
Photoemission
the emission of electrons from a material caused by light shining on it
Photon
the particle of electromagnetic radiation
Principle of reversibility
the principle of reversibility states that a ray of light will follow the same path in the opposite direction when it is reversed
Radioactive decay series
a chain of radioactive decays as a radioactive element changes to eventually become a stable, non-radioactive element
Radioisotope
short for radioactive isotope
Radionuclide
short for radioactive nuclide
Spectrometer
an instrument that can make precise measurements of the spectra produced by different light sources
Spontaneous fission
the random splitting of a large atomic nucleus due to the internal processes within the nucleus
Stopping potential
the minimum voltage required to reduce photoelectric current to zero
Threshold frequency
the minimum frequency of electromagnetic radiation that will cause photoemission for a particular substance
Total internal reflection
when a ray of light travelling in a more dense substance meets a boundary with a less dense substance at an angle greater than the critical angle, the ray is not refracted but is all reflected inside the more dense substance
Valence shell
the atomic energy level that contains the outermost electrons of the atom. It is the electrons in this shell that determine the chemical reactions between elements.
Work function
the minimum energy required to cause photoemission from a particular substance
