Answer: 1/r 2.
- A r
- B 1/r
- C 1/r<sup>2</sup>
- D 1/r<sup>3</sup>
Correct answer: C. 1/r<sup>2</sup>
Explanation: Sound intensity follows inverse square law: I proportional to 1/r<sup>2</sup> (energy spreads over 4*pi*r<sup>2</sup>).
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.