A photon has energy, wavelength, and frequency properties. Light's wavelength can be measured using a tool called a spectroscope or a spectrometer. As an object heats up, it gets brighter because it emits more electromagnetic radiation. The dominant color or wavelength of the emitted radiation changes with temperature. Intensity depends greatly on temperature of the black body.
Light does the same thing.
If object is moving towards you, the wavelengths get smaller as the waves are compressed and you get a BLUE shift. If the object is moving away from you, the waves are expanded and the wavelengths are longer and you get a RED shift. The farther away a galaxy is, the faster it is moving away from us. A song about Doppler Shifts Kirchhoff's Laws. summary . A luminous solid, liquid or dense gas emits light of all wavelengths and produces a continuous spectrum.