Two types of graphs are commonly used to depict waves:
- Displacement-position graph: which shows a “snap-shot” of the entire wave profile at one particular instant in time.
- Displacement-time graph: which shows the oscillation of one particular point on the wave.
If the displacement-position graph below is for a rightward traveling wave at , sketch the displacement-time graphs for the oscillations at position A and B.
Deduce the direction of motion at A, if the graph is
a) a displacement-position graph of a wave traveling rightward.
b) a displacement-time graph.
Assume that positive displacement is upward, and negative displacement is downward.
Since this is a displacement-position graph, A is a particular point on the wave. By mentally “animating” the wave profile rightward, we can deduce that point A is having a downward motion at this instant in time.
Since this is a displacement-position graph, A is a particular instant in time. At this instant, the oscillation’s displacement is positive and becoming more positive. So the oscillation is having an upward motion at the instant A.