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A galaxy moving with speed 300km/s shows...

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

Text Solution

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Here, `v_("radial")=-300 km//s=-3xx10^(5)m//s`
Negative sign comes because we observe blue shift i.e., galaxy is approaching us.
Now, `-(Deltalambda)/(lambda)=-(v_("radial"))/c`
`rArr=-(Deltalambda)/(589.0 nm)=(-(-3xx10^(5)))/((3xx10^(8)))`
`rArr Delta lambda=-(589.0)xx10^(-3) nm`
=-0.589
Hence, the observed wavelength will be (589.0-0.589)nm =588.411 nm
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