Hi There. So the 'red shift' and the 'blue shift' are all apart of the Doppler shift. But they are polar opposites.
Question 1:
Red shift means the frequency and associated wavelength of visible light has shifted toward the red part of the spectrum of EM radiation, as opposed to blue shift which means the frequency and associated wavelength has shifted toward the blue part of the spectrum. Red shift is a lower frequency / longer wavelength, and blue shift is a higher frequency / shorter wavelength. You could be wondering what causes red shift, and there are a few reasons for it. One of the causes is relativistic motion, often known as the Doppler Effect, which was initially noticed with sound waves and moving observers and sources. The light looks redder as a source moves away from an observer (they move away from each other, regardless of which one is traveling with respect to some reference frame), and bluer as the two move closer to one another. The term gravitational red shift refers to another reason. As a photon (a quantum of EMR) moves away from the surface of a mass aggregation, such as a star, the intensity of the field's magnitude decreases by the square of the distance, and the photon accelerates. A photon experiences the reverse consequence as it passes through a g-field with a rising magnitude of pressure, but there is considerable disagreement over what happens to the little amount of kinetic energy obtained from the field. Gravitational red shift is then seen. EM in nature is another factor. The phosphor coating on the interior of the glass tube is struck by UV radiation that is emitted by the arc carried via the mercury vapor in fluorescent lamps. The UV photons' energy is absorbed by the phosphor coating, which subsequently emits heat and visible light. The transition from UV to visible light and heat is a classic red shift. The identical red shift phenomena is explained by three separate methods.
Question 2:
The displacement of the spectrum to shorter wavelengths in the light coming from distant celestial objects moving toward the observer. Ever notice the sound of a car or train is higher pitched when it's heading toward you, and becomes lower as it goes away? Light does the same thing. If you look at an object that's heading away from you quickly enough, it will appear more red than it actually is. If something is heading towards you, it will appear more blue. This becomes very useful for astronomers; if you know a certain object's composition, you can tell how fast it's moving by the color change.
Question 3:
The apparent difference between the frequency at which sound or light waves leave a source and that at which they reach an observer is known as the "Doppler effect," and it is caused by the relative velocity of the wave source and the observer. This phenomena is used in astronomical observations, Mössbauer effect studies, radar, and modern navigation. The earliest description of it was published in 1842 by Austrian scientist Christian Doppler. The apparent pitch of a blowing horn is a fantastic illustration of the Doppler effect since it increases as you move closer to it before decreasing as you pass it. Similar to this, when a star is observed from Earth, its light shifts toward the violet end of the spectrum (higher frequency or shorter wavelength) when the star and Earth are getting closer and toward the red end of the spectrum (lower frequency or longer wavelength) when the star and Earth are getting farther apart. The Doppler effect is often used in contemporary models of the cosmos to study stellar motion and search for double stars. see redshift as well.
Question 4:
Blueshift is the name for an object's light while it is travelling toward us, and redshift is the name for an object's light when it is going away from us.
Thank you,
Eddie