Sonar on ships uses the Doppler effect to detect:

  1. the depth only
  2. salinity
  3. water temperature
  4. the speed of moving submarines or shoals of fish
Answer

D) the speed of moving submarines or shoals of fish

Echo frequency is shifted by motion. SLO P-11-D-04 · Understanding

Physics MCQ · More Wave Intensity and the Doppler Effect MCQs · Practise