SQA Higher Physics Practice Exam

When two waves meet out of phase, their crests align with troughs of the other wave. This relationship results in cancellation of the wave amplitudes, which effectively reduces the overall intensity of the resultant wave. This phenomenon is known as destructive interference. In this scenario, the maximum positive displacement of one wave coincides with the maximum negative displacement of another, leading to a net displacement closer to zero. This is why the intensity—the power per unit area—is minimized. Destructive interference is a key concept in wave physics, illustrating how waves can interact in ways that diminish their overall effects when they do not synchronize positively. Understanding this concept also helps differentiate it from constructive interference, where waves are in phase and amplify one another, resulting in greater intensity. The other terms, resonance and destructive summation, are not standard terminology used to describe this specific interaction of waves and would not be appropriate in this context.