Answer: 9×.
- A 3×
- B 6×
- C 9×
- D 81×
Correct answer: C. 9×
Explanation: I ∝ A², so 3× amplitude gives 9× intensity.
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.