15.13 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:
(b) The given equation is not a periodic function. Therefore, it does not represent either a travelling wave or a stationary wave.
(c) The given equation represents a travelling wave as the harmonic terms 'kx' and 'ωt' are in the combination of (kx–ωt).
(d) The given equation represents a stationary wave because this equation actually represents the superposition of two stationary waves similar to