Answer: 20 cm.
- A 10 cm
- B 20 cm
- C 40 cm
- D 80 cm
Correct answer: B. 20 cm
Explanation: Consecutive nodes are separated by λ/2 = 40/2 = 20 cm.
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.