Wavelength
The wavelength of a wave is the distance between two neighbouring, identical parts of the wave. It is usually written with the Greek letter lambda (λ).[1] Wavelength is one of several properties shared by all waves, along with amplitude, period, frequency and energy.[2]
Measuring wavelength
A simple way to measure a wavelength is from one crest (high point) of a wave to the next.[3] The same idea applies to electromagnetic waves such as light, which have crests and troughs like ocean waves; the distance between their crests is the wavelength.[4]
Wavelength, speed and frequency
A wave travels forward by one wavelength in the time of one period, the time taken for one complete cycle, and its speed is the distance it travels in a given time.[5] The frequency of a wave is the number of crests that pass a given point each second.[6]
Electromagnetic waves
Electromagnetic waves come in a huge range of wavelengths. According to NASA, the shortest are only a fraction of the size of an atom, while the longest that scientists study can be wider than the Earth.[7] NASA notes that scientists describe different parts of the electromagnetic spectrum in different ways: radio waves and microwaves are usually described by their frequency, infrared and visible light by their wavelength in metres, and X-rays and gamma rays by their energy.[8]
References
- ↑ "16.9 Waves". College Physics 2e. OpenStax, Rice University. Retrieved 20 October 2026.
The water wave in the figure also has a length associated with it, called its wavelength λ, the distance between adjacent identical parts of a wave.
- ↑ "16.9 Waves". College Physics 2e. OpenStax, Rice University. Retrieved 20 October 2026.
Water waves exhibit characteristics common to all waves, such as amplitude, period, frequency and energy.
- ↑ "16.1 Traveling Waves". University Physics Volume 1. OpenStax, Rice University. Retrieved 20 October 2026.
the wavelength is shown measured between two crests
- ↑ "Anatomy of an Electromagnetic Wave". Tour of the Electromagnetic Spectrum. NASA Science. Retrieved 20 October 2026.
Electromagnetic waves have crests and troughs similar to those of ocean waves. The distance between crests is the wavelength.
- ↑ "16.9 Waves". College Physics 2e. OpenStax, Rice University. Retrieved 20 October 2026.
The speed of propagation vw is the distance the wave travels in a given time, which is one wavelength in the time of one period.
- ↑ "Anatomy of an Electromagnetic Wave". Tour of the Electromagnetic Spectrum. NASA Science. Retrieved 20 October 2026.
The number of crests that pass a given point within one second is described as the frequency of the wave.
- ↑ "Anatomy of an Electromagnetic Wave". Tour of the Electromagnetic Spectrum. NASA Science. Retrieved 20 October 2026.
The shortest wavelengths are just fractions of the size of an atom, while the longest wavelengths scientists currently study can be larger than the diameter of our planet!
- ↑ "Anatomy of an Electromagnetic Wave". Tour of the Electromagnetic Spectrum. NASA Science. Retrieved 20 October 2026.
Radio and microwaves are usually described in terms of frequency (Hertz), infrared and visible light in terms of wavelength (meters), and x-rays and gamma rays in terms of energy (electron volts).