Answer: Reflection of sound.
- A Refraction of sound
- B Reflection of sound
- C Diffraction of sound
- D Interference of sound
Correct answer: B. Reflection of sound
Explanation: Echo is the repetition of sound due to reflection from a distant surface.
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.