1.

What speed should a galaxy move with respect us to that the sodium line at 589.0nm is observed at 589.6nm?

Answer»

Solution :Since `v lambda= c`,
`(TRIANGLE v)/(v)= -(triangle lambda)/(lambda)` (for small changes in v and `lambda`).
For `triangle lambda= 589.6-589.0= +0.6nm`
we get [using Eq. (3.9)]
`(triangle v)/(v)= -(triangle lambda)/(lambda)= (-v_("raidial"))/(v)" or, "v_("RADIAL") cong +c ((0.6)/(589.0))`
`= +3.06xx 10^(5)ms^(-1)= 306 KM"/"s`
Therefore, the galaxy is movingaway from US.


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