DOPPLER BALL – RED SHIFT
Lesson Plan
KS4/5
Learning
objectives:

Recognise that we can deduce the direction of a star by observing the light that is emitted
from it.
Explain what the terms red shift and blue shift mean.
Describe what red shift and blue shift can tell us about the motion of a star.
Deduce information about the motion of a star from given spectra.
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
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Resources
Prior
Knowledge:

Lascells Doppler
 Student Worksheet
 Doppler Ball – Red
Ball
Shift Presentation
For this lesson it is assumed that students already have knowledge of the following syllabus
requirements: These could be reinforced as part of a starter activity.



Visible light is part of the electromagnetic spectrum.
That the electromagnetic spectrum consists of a range of wavelengths.
That red light has a longer wavelength than blue light.

Using miniature whiteboards or student notebooks ask students to decide what colour light
most stars emit. (The first slide on the presentation).

Remind students that white light consists of a spectrum of colours and explain that stars
emit a spectrum with absorption lines due to certain elements present within the star.

Explain the operation of the Doppler ball and while demonstrating ask students to describe
the sound that they hear.

Using the slide on the presentation explain the effect in terms of the wavelength of the
sound.

Challenge students to suggest what will happen to the wavelength of light detected from a
star that is travelling away from us.

Using the slide on the presentation explain the observed change in spectra for a star or
galaxy that is moving away from us. Introduce the students to the term ‘red shift’.

Challenge students to deduce information about the universe based on the observations.

Using the slide on the presentation explain the results of observations and the deductions
that can be made from them. (Students may benefit from some notes on this).

Challenge students to suggest what a spectrum showing absorption lines shifted towards
the blue end of the spectrum means for the motion of the star. Ask them to suggest what this
effect might be called.

Using the slide from the presentation explain the theory behind blue shift.

To summarise ask students to complete the summary questions on the worksheet.
(Answers are B, A+C, C)
Lesson Outline: