Which one of the following does not cause stationary waves?

مندرجہ ذیل میں سے کون سا ساکن لہروں کا سبب نہیں بنتا؟

Two waves of unequal amplitude

Two waves travelling in opposite directions

Two waves of equal frequency

Two waves of same speed

Two waves of unequal amplitude do not cause stationary waves.

Stationary waves are formed when two waves of equal amplitude, frequency, and speed travel in opposite directions and interfere with each other.