In a laboratory the balmer beta line has a wave length of 486.1 nm. if the line appears in the stars spectrum?

Question

in a laboratory the balmer beta line has a wvae length of 486.1 nm. if the line appears in the stars spectrum at 486.3 nm, what is the stars radial velocity. is it approaching or receding??

please explain!!! how this question is worded is confusing me.

Answer 1

I suggest you read your textbooks. There is nothing confusing about the question at all.

Answer 2

There is nothing confusing about this. Apply the equations for Doppler shift and read off the answer.