Differences Between Doppler Effect Formulas: u & f´

[camel-man]

u = (v + u') / (1 + v u' / c2)

f´ = f √ [ ( 1 + v / c) / ( 1 – v / c) ]What are the difference between these two formulas? My formula sheet doesn't specify the two. I believe one of them has to do with doppler effect.

 

[PAllen]

First is colinear relatavistic velocity addition. Second is frequency change due to Doppler for a source emitting at f approaching a detector at v; f' is the frequency that will be be measured by the detector.

 

[camel-man]

Thank you so much PAllen