Explain why the displacement A sin (k.r wt) at position r and time t is called

Question:

Explain why the displacement A sin (k.r – wt) at position r and time t is called a plane wave. In which direction does it travel? A wave displacement is y = 0.5 sin (0.1 x – 0.4t), where all quantities are in SI units. Determine.
(a) The wave amplitude,
(b) The wavelength,
(c) The time period,
(d) The wave velocity,
(e) The acceleration a of the displacement.
Sketch graphs of y and a at t = 0 for x in the range 0 to 100 m.