Doppler effect

Nature of science:

Technology: Although originally based on physical observations of the pitch of fast moving sources of sound, the Doppler effect has an important role in many different areas such as evidence for the expansion of the universe and generating images used in weather reports and in medicine. (5.5)

• The Doppler effect for sound waves and light waves

Applications and skills:

• Sketching and interpreting the Doppler effect when there is relative motion between source and observer
• Describing situations where the Doppler effect can be utilized
• Solving problems involving the change in frequency or wavelength observed due to the Doppler effect to determine the velocity of the source/observer

Guidance:

• For electromagnetic waves, the approximate equation should be used for all calculations
• Situations to be discussed should include the use of Doppler effect in radars and in medical physics, and its significance for the red-shift in the light spectra of receding galaxies

Data booklet reference:

• Radar usage is affected by the Doppler effect and must be considered for applications using this technology

Theory of knowledge:

• How important is sense perception in explaining scientific ideas such as the Doppler effect?

Utilization:

• Astronomy relies on the analysis of the Doppler effect when dealing with fast moving objects (see Physics option D)

Aims:

• Aim 2: the Doppler effect needs to be considered in various applications of technology that utilize wave theory
• Aim 6: spectral data and images of receding galaxies are available from professional astronomical observatories for analysis
• Aim 7: computer simulations of the Doppler effect allow students to visualize complex and mostly unobservable situations