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 (100 πt + 0.5x)
State which of these represent
(a) a travelling wave along -x direction
(b) a stationary wave
(c) beats
(d) a travelling wave along +x direction
Give reasons for your answers
(a) When a wave travels in (-x) direction, it must have +kx which is given as:
(d) y = 100 cos (100 πt + 0.5x)
(b) When a stationary wave is there then,
(a) y = 5 cos (4x) sin (20t)
(c) When beats are involved
(c) y = 10 cos [(252-250)πt] cos [(252+250) πt]
(d) a travelling wave along +x direction is
(b) y = 4 sin (5x-t/2) + 3 cos (5x-t/2)
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