5.6.169 - Doppler effect

Understand how the movement of a source of waves relative to an observer/detector gives rise to a shift in frequency (Doppler effect).

Use - doppler effect to connect the rule to the data and decision in the question.

This matters because - doppler effect determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply - doppler effect to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: - Doppler effect is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.