Given below are some functions of x and t to represent the displacement of an elastic wave.
(a) y = 5 cos (4x ) sin (20t )
(b) y = 4 sin (5x – t/2) + 3 cos (5x – t/2)
(c) y = 10 cos [(252 – 250) πt ] cos [(252+250)πt ]
(d) y = 100 cos (100πt + 0.5x )
State which of these represent
(a) a travelling wave along –x direction
(b) a stationary wave
(d) a travelling wave along +x direction.
Given reasons for your answers.