Spectral lines from galaxy b are redshifted from their rest wavelengths twice as much as the spectral lines from galaxy a. according to hubble's law, what can you say about their approximate relative distances?
a. galaxy a is twice as far as galaxy b.
b. galaxy b is four times as far as galaxy a.
c. galaxy a is four times as far as galaxy b.
d. galaxy b is twice as far as galaxy a.
e. not enough information to say

a. Galaxy A is twice as far as Galaxy B.

Explanation:

The correct answer is  Galaxy A is twice as far as Galaxy B. that is option a.

This can be explained as per the Hubble's law, The more the distance between two galaxies the faster they are moving away from each other. It is given that red shift of galaxy A is twice as that of B. This means that A is twice as far B.

Note: When an object moves away from us the light is shifted to the red end of the spectrum.

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