Superposition in Stationary Waves

Steps:

• Stationary wave displacement y equals sum of two progressive waves: y = y1 + y2.
• Given y and y1 from graph, solve for y2 = y - y1 at each point.
• At J: y ≈ 0 mm, y1 ≈ +5 mm, so y2 ≈ -5 mm.
• At K: y ≈ 0 mm, y1 ≈ 0 mm, so y2 ≈ 0 mm; at L: y ≈ 0 mm, y1 ≈ +10 mm, so y2 ≈ -10 mm.

Why A is correct:

• Matches y2 = y - y1, the algebraic difference required by wave superposition principle.

Why the others are wrong:

• B: Incorrect signs and magnitudes; ignores subtraction for opposite-direction waves.
• C: Option incomplete/missing; cannot evaluate.
• D: Wrong values at J and L; assumes addition instead of difference.

Final answer: A