Wavelength is the distance between two consecutive points in a wave that are in phase, such as from crest to crest or trough to trough. It is commonly measured in meters and is a key characteristic of waves, including sound waves, light waves, and water waves. Wavelength helps determine the wave's properties, such as its frequency and energy. In the context of electromagnetic waves, such as those produced by the sun or radio transmitters, different wavelengths correspond to different types of radiation. For example, visible light has wavelengths ranging from about 400 to 700 nanometers, while radio waves have much longer wavelengths, often measured in meters or kilometers.