Whole lotta 'quivocation goin' on! Let's nail down some terms:
Deflecting a light beam by bouncing it off a mirror is called '
reflection'.
Changing the path of a light beam is called '
deflection'.
Deflecting a light beam by passing it through a medium is called '
refraction'.
Splitting a beam of white light into its spectral components by passing it through a prism is called '
diffraction'.
Removing parts of the spectrum is called '
filtration'.
Scattering light is called '
diffusion'.
The sky is blue because dust and nitrogen molecules in the Earth's atmosphere scatter the blue light from the sun, but let the longer wavelengths pass through. The reddening of the sun's light at sunrise and sunset is caused by the sun's light passing through more of the Earth's atmosphere during those times than at mid-day, thus scattering most of the wavelengths shorter than red.
The
Doppler Effect produces a red-shifted or blue-shifted spectrum, and while the Doppler Effect has been observed in both sound and light, the audio and video spectra are not the same thing -- sound is the result of rapidly changing pressure in a solid, liquid or gaseous medium, while light is the result of rapidly oscillating quanta. Sound requires matter to propagate, while light does not require any medium at all to propagate.
The Doppler Effect changes the apparent wavelength of light.
Red shift, for example, can be caused by relative axial motion between the light source and the observer, an intense gravity field at the light source, or the general expansion of the universe.
