Stationary waves are result of _ travelling in opposite direction waves.

Explanation

Stationary waves, or standing waves, are formed when two waves of the same amplitude and frequency travel in opposite directions along the same medium and interfere with each other. This interference results in a pattern of nodes (points of no motion) and antinodes (points of maximum motion), creating a wave pattern that appears to be standing still. This phenomenon is crucial in musical instruments, where the vibration of strings or air columns produces sound.Option A is correct because it accurately describes the condition for forming stationary waves: two identical waves traveling in opposite directions. Option B is incorrect because different waves cannot produce the consistent interference pattern needed for stationary waves. Option C is incorrect because it implies that both identical and different waves can form stationary waves, which is not true. Option D is incorrect because it falsely claims that stationary waves cannot be formed.