What is resonance in wave behavior?

Resonance in wave behavior specifically refers to the phenomenon where a system experiences a significant increase in amplitude when it is driven at or near its natural frequency. Every system has a natural frequency, which is the frequency at which it oscillates most efficiently. When an external force is applied to the system at this frequency, it can cause the amplitude of the oscillations to increase dramatically, resulting in what is termed resonance.

This is observed in various physical systems, such as musical instruments, where striking a string causes it to vibrate at its natural frequency, producing sound. Similarly, bridges can vibrate dangerously if wind or traffic creates forces that match their natural frequency.

The other options do not correctly describe resonance. A decrease in wave frequency over time does not encapsulate the concept of resonance. A shift in the phase of a wave refers to the positional change of a wave in relation to a reference point, which is not the same as resonance. The reflection of waves off surfaces describes a different wave behavior known as reflection, unrelated to the amplitude increase characteristic of resonance.