Final answer:
At the half-frequencies, the interference pattern changes in a wave, leading to regions of destructive interference instead of constructive interference.
Step-by-step explanation:
The power at the half-frequencies in a wave depends on the concept of interference. When two waves of the same frequency but opposite phase interfere with each other, they can create regions of constructive and destructive interference. At the half-frequencies, also known as the second harmonics, the interference pattern changes. The regions of constructive interference, where the waves are in phase and amplify each other, become regions of destructive interference, where the waves are out of phase and cancel each other out.