Principle of Superposition Adds Wave Displacements

Steps:

• Recall that the principle of superposition applies to linear waves, where overlapping waves combine linearly.
• Identify the key quantity: when waves meet, their effects add point by point.
• Note that displacement represents the wave's position deviation from equilibrium at that point.
• Conclude the added quantity is displacement, as amplitudes, intensities, and wavelengths do not sum directly.

Why B is correct:

• The principle defines superposition as the total displacement being the vector sum of individual wave displacements, per the wave equation solution for linear systems.

Why the others are wrong:

• A: Amplitude is the maximum displacement magnitude, which emerges from summed displacements but is not the added quantity.
• C: Intensity is energy flux proportional to amplitude squared, added only for incoherent waves, not superposition.
• D: Wavelength is the spatial period of a wave, unchanged by superposition.

Final answer: B