Question

A star rotating at a fast speed gives a ____ spectral line because light is red-shifted and blue-shifted _____ from the center.

a) Narrow, closer
b) Broad, closer
c) Narrow, farther
d) Broad, farther

Answer 1

A rapidly rotating star produces a broad spectral line due to the Doppler effect, which causes light to be red-shifted and blue-shifted farther from the center, indicating its rotation speed.

Step-by-step explanation:

A star rotating at a fast speed gives a broad spectral line because light is red-shifted and blue-shifted farther from the center. This is a result of the Doppler effect, where the side of the star rotating toward us shifts the spectral lines to shorter wavelengths (blue-shifted), and the side rotating away from us shifts the spectral lines to longer wavelengths (red-shifted). Because each point on the star has its own Doppler shift due to its motion, the cumulative effect when observing the entire star is a broadening of the spectral lines. This broadening is indicative of the rotation speed of the star.