Answer: X-rays.
- A Sound
- B Water waves
- C X-rays
- D Seismic waves
Correct answer: C. X-rays
Explanation: X-rays are electromagnetic waves: they do not need a medium. Sound, water, and seismic waves are all mechanical.
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.