Dark line in an otherwise continuous bright spectrum, where light within one narrow frequency range has been removed.
Spectrum in which the radiation is distributed over all frequencies, except at a few specific frequencies. It is produce by light from a continuous spectrum source that passes through a low density gas. The gas absorbs the same frequencies that it would emit if heated.
Building block of matter, composed of positively charged protons and neutral neutrons in the nucleus, surrounded by negatively charged electrons.
The continuous spectrum emitted by a blackbody. The flux at each wavelength is given by a formula known as Planck's Law.
Broadening of spectral lines due to collisions between atoms, most often seen in dense gases.
Spectrum in which the radiation is distributed over all frequencies, not just a few specific frequency ranges. A prime example is the black-body radiation emitted by a hot, dense body.
Any motion-induced change in the observed wavelength (or frequency) of a wave.
Matter made up of one particular atom. The number of protons in the nucleus of the atom determines which element it represents.
Technically, a particle that cannot be subdivided into component parts; however, the term is also often used to refer to particles such as protons and neutrons, which are themselves made up of quarks.
Bright line in a specific location of the spectrum of radiating material, corresponding to emission of light at a certain frequency. A heated gas in a glass container produces emission lines in its spectrum.
State of an atom when one of its electrons is in a higher energy orbital than the ground state. Atoms can become excited by absorbing a photon of a specific energy, or by colliding with a nearby atom.
The lowest energy state that an electron can have within an atom.
Term describing the number of electrons missing from an atom: I refers to a neutral atom, II refers to an atom missing one electron, and so on.
State of an atom that has had at least one of its electrons removed. This charged atom is refered to as an ion.
Three rules governing the formation of different types of spectra.
A tightly bound collection of atoms held together by the electromagnetic fields of the atoms. Molecules, like atoms, emit and absorb photons at specific wavelengths.
An elementary particle with roughly the same mass as a proton, but which is electrically neutral. Along with protons, neutrons from the nuclei of atoms.
(i) Dense, central region of an atom, containing both protons and neutrons, and orbited by one or more electrons. (ii) The solid region of ice and dust that composes the central region of the head of a comet. (iii) The bright central region of a galaxy.
One of several energy states in which an electron can exist in an atom.
Experiment concerning the detection of electrons from a metal surface, whose speed off the surface was dependent on the frequency of light striking the surface. The theoretical explanation rests on viewing light as made up of photons, or individual "bullets" of energy.
Individual packet of electromagnetic energy that makes up electromagnetic radiation.
The fact that light and matter on small scales behave in a discontinuous manner, and manifest themselves in the form of tiny "packets" of energy, called quanta.
The laws of physics as they apply on atomic scales.
Instrument used to view a light source so that the light is split into its component colors.
The study of the way in which atoms absorb and emit electromagnetic radiation. Spectroscopy allows astronomers to determine the chemical composition of stars.
Light that has been separated into its component colors.
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