Concept:The time taken between two points on a wave is found by counting the number of complete oscillations between them and multiplying by the period
T.
Explanation:Frequency is the number of oscillations per second, while period
T is the time for one complete oscillation.
From the diagram, the wave between P and Q covers two complete oscillations.
Each complete oscillation takes one period
T.
Therefore, the total time taken is
t=2×T=2T.
This is equal to 2 periods.
Answer:A. 2 periods
