what type of doppler shift is observed when a wave source?

Question

approaches an observer ?

a)redshift b)blueshift

recedes from an observer?

a)redshift b)blueshift

Answer 1

Red Shift = going away
Blue Shift = coming toward you

When sound waves or light is heading toward you and going fast the waves bunch up and shift down on the frequency chart as a blue shift.
When sound waves or light is heading away from you and going fast the waves spread out and shift up on the frequency chart as a red shift.

According to Wikipedia: http://en.wikipedia.org/wiki/Redshift
“In physics and astronomy, redshift occurs when the electromagnetic radiation, usually visible light, that is emitted from or reflected off an object is shifted toward the (less energetic) red end of the electromagnetic spectrum. More generally, redshift is defined as an increase in the wavelength of electromagnetic radiation received by a detector compared with the wavelength emitted by the source. This increase in wavelength corresponds to a decrease in the frequency of the electromagnetic radiation. Conversely, a decrease in wavelength is called blue shift.
Any increase in wavelength is called "redshift", even if it occurs in electromagnetic radiation of non-optical wavelengths, such as gamma rays, x-rays and ultraviolet. This nomenclature might be confusing since, at wavelengths longer than red (e.g., infrared, microwaves, and radio waves), redshifts shift the radiation away from the red wavelengths.”

According to Wikipeidia: http://en.wikipedia.org/wiki/Blue_shift
“Blueshift refers to a shortening of a transmitted signal's wavelength, and/or an increase in its frequency. The name comes from the fact that the shorter-wavelength end of the optical spectrum is the blue (or violet) end, hence, when visible light is compacted in wavelength, it is "shifted towards the blue", or "blue-shifted". Since the longer-wavelength end of the visible electromagnetic spectrum is red, the opposite effect, of a lengthening of a signal's wavelength, is referred to as redshifting.”

When the astronomer Hubble observed the Red Shift of stars he formulated his theory that the universe is expanding which became the root of the big bang theory.

We know that the most common ingredient in stars is hydrogen and each element burns at a unique combination of spectral colors. So when we see burning hydrogen and it is shifted then we have an idea of how fast that star is moving away from us. This is one of the “yard sticks” that astronomers use to measure the universe. We know it has to be true since there isn’t an element lower than hydrogen on the periodic table, so the color spectrum we observe has to be either red or blue shifted. Hydrogen is the most common element in the Universe, and most stars are full of it.

Answer 2

That would depend on the definition of redshift and blueshift. These are terms that someone has come up with to benifit thier own bank account. In the Doppler effect the pitch raises and the wave lenght shortens as the source nears; then the opposite as it departs!

Answer 3

It's a blueshift (increasing frequency) if the distance between the source and observer is decreasing and a redshift (decreasing frequency) if the distance is increasing.

Doug

Answer 4

b
then
a