CoachDense, hot matter — the filament of a bulb, molten steel, the surface of a star — glows, and its light contains every wavelength over a wide range: an unbroken band of color with nothing missing. Such a spectrum is a continuous spectrum. It carries no trace of the chemical nature of the body: a white-hot iron bar and a white-hot copper bar glow alike. What it does encode — entirely — is the temperature.
Examples
Example 2.9 (Taking the Sun’s temperature)
The Sun’s continuous spectrum is most intense near . Wien’s law gives its surface temperature:
about — measured from million kilometers away, with a prism and a division.