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 can only travel through a material. It will travel through air, through walls (and other solid objects), and through water and other liquids. On the other hand, a light wave is not made of vibrating particles. It is a wave of changing electric and magnetic fields which can exist in a vacuum.