question_answer 13)

Given below are some functions of x and t to represent the displacement (transverse or longitudinal) of an elastic wave. State which of these represent (i) a travelling wave, (ii) a stationary wave or  (iii) none at all?                 (a)                 (b)                 (c)                 (d)  

Answer:

(a) It represents a stationary wave as harmonic functions of; x and t are contained separately in the equation. (b) It cannot represent any type of wave. (c) It represents a progressive/travelling harmonic wave. (d) This equation is sum of two functions each representing a stationary wave. Therefore, it represents superposition of two stationary waves.