Answer: 336 m/s.
- A 320 m/s
- B 300 m/s
- C 352 m/s
- D 336 m/s
Correct answer: D. 336 m/s
Explanation: The gap between consecutive resonances is λ/2 = 0.62 - 0.20 = 0.42 m, so λ = 0.84 m. Then v = fλ = 400 × 0.84 = 336 m/s.
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.