whose equations are related to this mentioned radiation?
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what is referred to as redshift? It is a phenomenon where electromagnetic radiation (such as light) from an object undergoes an increase in wavelength.
wiki:25663002
Redshift [SEP] Introduction
In physics, redshift is a phenomenon where electromagnetic radiation (such as light) from an object undergoes an increase in wavelength. Whether or not the radiation is visible, "redshift" means an increase in wavelength, equivalent to a decrease in wave frequency and photon energy, in accordance with, respectively, the wave and quantum theories of light. Neither the emitted nor perceived light is necessarily red; instead, the term refers to the human perception of longer wavelengths as red, which is at the section of the visible spectrum with the longest wavelengths. Examples of redshifting are a gamma ray perceived as an X-ray, or initially visible light perceived as radio waves.