In fo = fs vv pm vs, the minus sign is used when the source:

  1. is stationary
  2. moves towards the observer
  3. moves perpendicular
  4. moves away from the observer
Answer

B) moves towards the observer

Smaller denominator gives a higher frequency. SLO P-11-D-03 · Application

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