F1 and F2 denote the apparent frequencies of a sound source moving with the relative speed v for source-observer separating and approaching each other respectively. The ratio F1/F2 is:
1
\(\sqrt{\dfrac{(1-v^2/c^2)}{(1+v^2/c^2)}}\)
2
\(\sqrt{\dfrac{(1+v^2/c^2)}{(1-v^2/c^2)}}\)
3
\((1-v^2/c^2)(1+v^2/c^2)\)
4
\((1+v^2/c^2)(1-v^2/c^2)\)