Wave

A wave (also called hirr) is a disturbance in a medium or space that transmits energy and information from place to place. The energy carried depends on the wave's form, not on the medium or air itself: each particle of the medium oscillates around its fixed position while the wave itself propagates forward.

Waves are fundamental concepts in physics. They describe sound, light, seismic waves, ocean waves, and also the behavior of very small objects such as electrons. Measurable properties include wavelength (the distance between two identical points), frequency (the number of wave cycles per unit time), amplitude, and the speed of propagation.

Types of waves

Depending on what medium is needed, waves fall into two categories. Mechanical waves require a substance to travel through, such as sound which cannot travel in a vacuum. Electromagnetic waves, such as light, radio, and X-rays, travel through empty space at a constant speed.

Depending on the direction of disturbance, there are transverse waves whose particles oscillate perpendicular to the direction of travel, like vibrations in a stretched string, and longitudinal waves whose oscillations occur in the direction of travel, such as sound consisting of compressions and rarefactions of air.

Key behaviors

Waves exhibit characteristic behaviors. Reflection occurs when a wave bounces off a surface. Refraction is a change of direction when a wave enters a different medium with a different propagation speed. Diffraction is the spreading of a wave through a small opening or around an obstacle. Interference occurs when two waves meet at the same location, and their amplitudes either reinforce or cancel each other. The difference in speed between a source and observer creates the Doppler effect in sound.

Wave–particle duality

Quantum physics has shown that small objects such as light and electrons sometimes behave as waves and sometimes as particles. This is called wave–particle duality and is fundamental to understanding atomic structure.