Lesson: Redshift Physics • 9th Grade

In this lesson, we will learn how to calculate the radial velocity of a star or galaxy using the amount by which absorption lines in the spectrum of light from it are shifted.

Lesson Video

Sample Question Videos

04:22
03:45

Lesson Worksheet

Q1:

The diagram shows the spectral lines in the light from two galaxies, as well as the same spectral lines in the light from a laboratory source.

How is Galaxy A moving relative to Earth?

How is Galaxy B moving relative to Earth?

Which galaxy is moving faster relative to Earth?

Q2:

The diagram shows the absorption lines in a spectrum from a distant star compared to those in a spectrum from a laboratory sample. How is the star moving relative to Earth?

Q3:

An astronomer looks at the absorption lines in the spectrum of light coming from a distant galaxy. He identifies the absorption lines of hydrogen, which makes up most of the galaxy. He then compares these lines to the same absorption lines from a laboratory sample. His results are shown in the diagram.

How is the galaxy moving in relation to Earth?