Answer: Increases.
- A Decreases
- B Increases
- C Stays same
- D First increases then decreases
Correct answer: B. Increases
Explanation: As source approaches, wave fronts are compressed. Higher frequency (higher pitch) is heard. This is the Doppler effect.
A standing wave forms from two identical waves travelling in opposite directions and interfering; nodes (always zero displacement) and antinodes (maximum displacement) stay fixed in place, unlike a travelling wave where the whole pattern moves.
Concept context
Wave types, superposition, standing waves, Doppler effect, and sound intensity.