Aspectral line that appears at a wavelength of 321 nm in the laboratory appears at a wavelength of 328 nm in the spectrum of a distant object. we say that the object's spectrum is:

We say that the object's spectrum is shifted.

Explanation:

Spectral lines will be shifted to the blue part of the spectrum1 if the source of the observed light is moving toward the observer, or to the red part of the spectrum when is moving away from the observer (that is known as the Doppler effect).

That shift can be used to find the velocity of the object by means of the Doppler velocity.

 (1)

Where is the wavelength shift, is the wavelength at rest, v is the velocity of the source and c is the speed of light.

blue light is scattered in different directions by the tiny molecules of air. blue is scattered more than other colours because it has a shorter distance to travel which results in smaller waves. this is why we see a blue sky most of the time.