Two wave pulses, one rectangular and other triangular, approach each other as shown in the figure below.
They overlap at the point P at time $t$. The diagram best representing the appearance of the wave pulses at a time $t' \gt t$ is
Show Hint
Remember that wave pulses are not particles; they do not bounce off each other.
They pass through each other as if the other wave was not even there, keeping their original shape, speed, and orientation.
Step 1: Recall what pulses do when they meet. Two pulses moving toward each other simply pass through one another. While they overlap they add up, but afterward each one carries on exactly as before.
Step 2: State the superposition idea simply. The displacement at any spot is just the sum of the two individual pulse heights at that spot. The pulses do not damage or reshape each other permanently.
Step 3: Look at the moment of overlap at P. At time $t$ the rectangular and triangular pulses sit on top of each other, giving a combined shape that is taller while they coincide.
Step 4: Move forward to a later time. By the later time $t'$ the two pulses have separated again and moved past each other in their original travel directions.
Step 5: Recover the original shapes. The rectangular pulse is still a clean rectangle and the triangular pulse is still a clean triangle, completely unchanged in shape and size.
Step 6: Match to the figure. The correct diagram is the one showing both pulses fully restored to their starting forms, now on the opposite sides of where they crossed. \[ \boxed{\text{Both pulses emerge unchanged (option A)}} \]
