The primary responsibilities of human resources are: 1  C - Compensation. 2  H - Human resource development. 3  E - Employee and labor relations. 4  S - Safety and health. 5  S - Staff.
A new technique uses sound waves to levitate objects and move them in mid-air. Credit: Dimos Poulikakos View full size image. View full size image. Hold on to your wand, Harry Potter: Science has outdone even your best Leviosa! levitation spell.
Sound waves are like light and water waves in other ways too. When water waves traveling long distances across the ocean flow around a headland or into a bay, they spread out in circles like ripples. Sound waves do exactly the same thing, which is why we can hear around corners. Imagine you're sitting in a room off a corridor and, much further up the corridor, there's an identical room where someone is practicing a trumpet inside. Sound waves travel out from the trumpet, spreading out as they go.