continuspectrum

Continuous spectrum, sometimes spelled continuspectrum in some texts, refers to a spectrum that shows no gaps or discrete lines across a range of wavelengths. It contrasts with line spectra, which display isolated wavelengths arising from atomic transitions, and with band spectra, where molecular transitions create groups of lines that blend into bands.

It arises from sources that emit a broad, featureless distribution of photons. A classical example is a blackbody radiator, where thermal agitation produces emission at all wavelengths with intensity governed by temperature (Planck's law). Incandescent solids, liquids, and dense gases at high temperature also produce continuous spectra. In addition, light from very hot plasmas or from stellar photospheres can appear continuous over wide ranges because many transitions overlap.

In practice, instrumental resolution and intervening media can modify an intrinsic continuous spectrum, but a genuine continuous spectrum lacks the sharp spectral lines characteristic of atomic or molecular transitions. Some spectra are described as quasi-continuous when many lines are so closely spaced that they appear as a smooth curve.

Applications and significance include using the spectrum’s shape and peak to infer temperature and emissivity, through Wien’s law and Planck’s law. Continuous spectra are essential in calibrating instruments, studying the thermal properties of materials, and interpreting astronomical objects, where they provide information about temperature, composition, and physical conditions of emitters.