Periodic waves are disturbances that repeat at regular intervals over time and space. They can be found in various forms, such as sound waves, light waves, and water waves. The key characteristics of periodic waves include their wavelength, frequency, and amplitude, which help define their behavior and energy. The wavelength is the distance between two consecutive points in phase, such as crest to crest or trough to trough. Frequency refers to how many cycles occur in a given time period, usually measured in hertz (Hz). Amplitude indicates the maximum displacement from the rest position, affecting the wave's energy and intensity.