From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 486.1 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 485.9 nm. What can we conclude

We conclude that star moving toward observer.

Explanation:

According to the theory of doppler effect of light.

There are two kind of shift 1 )  Blue shift 2 ) Red shift, in which

1 ) if source of light moving toward observer so the apparent frequency of light increase( wavelength decrease ). This is which we call blue shift

2 ) if the distance between source and observer is increase, so the apparent frequency of light decrease ( wavelength increase ). This is which we call red shift.

Here, in our case wavelength of H-star is decrease so we can say that star moving toward observer ( Blue shift ).

the second one and the forth one are in the purple because they are opinions and the rest are in the yellow

explanation:

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