What speed should a galaxy move with respect to us so that the sodium line at `589.0 nm` is observed at `589.6 nm` ?
What speed should a galaxy move with respect to us so that the sodium line at `589.0 nm` is observed at `589.6 nm` ?
A. `106kms^(-1)`
B. `306kms^(-1)`
C. `513kms^(-1)`
D. `50kms^(-1)`
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Correct Answer - B
Since `vlamda=cand (Deltav)/v=(Deltalamda)/lamda` (for small changes in v and `lamda`)
where v is velocity, c is speed of light, `lamda` is wavelength and v is frequency.
`"For"" "Deltalamda=(589.6-589)nm=+0.6nm`
`therefore" "(Deltav)/v=(Deltalamda)/lamda=(v_("radial"))/c`
`rArr" "v_("radial")-=+c(0.6/589)=+3.06xx10^(5)ms^(-1)`
`=306kms^(-1)`
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