Question

You view a visible light spectrum from a star. The spectrum has dark lines that seem to match the transitions of hydrogen. However, they are at a slightly longer wavelength than expected. What is most likely, based on this spectrum?

a) The star is moving away from us
b) The star is moving towards us
c) The instrument has a calibration error
d) The star has an unusual chemical composition

Answer 1

The observation of hydrogen spectral lines at longer wavelengths indicates that the star is moving away from Earth due to the Doppler effect, making option (a) the correct answer.

Step-by-step explanation:

When we observe a visible light spectrum from a star with dark lines at longer wavelengths than expected for hydrogen transitions, it indicates that the star is moving away from us. This is a result of the Doppler effect, where the movement of a star towards or away from us changes the observed wavelength of its spectral lines. If the lines are shifted to longer wavelengths (redshifted), the star is receding; if they are shifted to shorter wavelengths (blueshifted), it is approaching. Considering the provided information, option (a) The star is moving away from us is the most likely explanation for the observed longer wavelengths.