A galaxy moving with speed 300km/s shows blue shift. At what wavelength sodium line at 589.0 nm will be observed ?

Explanation

Here, `v_("radial")=-300 km/s =- 3 xx 10^(5)m//s`
Negative sign comes because we observe blue shift i.e., galaxy is approaching us .
Now , `- (Delta lambda)/(lambda) = -(v_("radial"))/(c)`
`rArr - (Deltalambda)/(589.0nm) = (-(-3 xx 10^(5)))/((3xx 10^(8)))`
`rArr Delta lambda = - (589.0) xx 10^(-3) nm = - 0.589nm`
Hence, the observed wavelength will be (589.0-0.589) nm = 588.411 nm