Can someone explain EK's Doppler equations

[sicboy188]

or at least tell me if i have the subscripts right:

∆f/fsource = vrel/vlight or sound = ∆λ/λsource
where ∆f = |fobserved - fsource| and ∆λ = |λobserved - λsource|

is is vrel the relative velocity the source is to the observer?

EK's description doesn't really go into great detail on what is what. just wanna make sure i have this sorted.

thanks

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[tncekm]

vrel is the relative difference in velocity between the source and the observer.

the vlight/sound/etc is just the v of the medium; just whatever velocity the wave propagates at.

Whether you add the change in frequency or subtract it to the actual frequency (or wavelength) depends on whether or not the source and observer are approaching or leaving each other. Approaching means an increased frequency and a decreased wavelength, leaving means a decreased frequency and an increased wavelength.

The important thing to notice is just that the change in frequency or change in wavelength / actual wavelength is directly proportional to the relative difference in velocities of the source and observer / the speed of the wave as it propagates.

So, if df/f = v/c and v = 1/10c, then df/f = 1/10.

 

[sicboy188]

wow.. realy well explained! i understand the phenomena conceptually, but didnt know how to apply that understanding to the equation.

thanks!