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?
A)The star is moving toward us.
B)The star is moving away from us.
C)The star is getting hotter.
D)The star is getting colder.
E)The "star" actually is a planet.

Question

Quizplus · Accepted Answer

The observed shift in the wavelength of the hydrogen line from its laboratory value to a shorter wavelength (from 486.1 nm to 485.9 nm) indicates a blueshift, which means the star is moving toward us.

From Laboratory Measurements,we Know That a Particular Spectral Line Formed