Related topics: light · laser · galaxies · physical review letters · stars

Smart windows that self-illuminate on rainy days

Smart windows that automatically change colors depending on the intensity of sunlight are gaining attention as they can reduce energy bills by blocking the sun's visible rays during summer. But what about windows that change ...

A tale of two telescopes: WFIRST and Hubble

NASA's Wide Field Infrared Survey Telescope (WFIRST), planned for launch in the mid-2020s, will create enormous cosmic panoramas. Using them, astronomers will explore everything from our solar system to the edge of the observable ...

VLASS: A survey of the radio sky

Technological advances in recent years have increased the sensitivity of radio interferometers like the Karl G. Jansky Very Large Array (VLA) to the radio emission from astronomical sources in their continuum (not only in ...

Astronomers measure wind speed on a brown dwarf

Astronomers have used the National Science Foundation's Karl G. Jansky Very Large Array (VLA) and NASA's Spitzer Space Telescope to make the first measurement of wind speed on a brown dwarf—an object intermediate in mass ...

Team develops foldable and washable luminescent film

Infrared radiation, which is invisible yet highly utilizable, is used in various fields and for various purposes, such as for coronavirus detection (i.e. through thermal imaging cameras and biosensors). A Korean research ...

page 1 from 87


In physics, the wavelength of a sinusoidal wave is the spatial period of the wave – the distance over which the wave's shape repeats. It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a characteristic of both traveling waves and standing waves. Wavelength is commonly designated by the Greek letter lambda (λ). The concept can also be applied to periodic waves of non-sinusoidal shape. The term wavelength is also sometimes applied to modulated waves, and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids.

Assuming a sinusoidal wave moving at a fixed wave speed, wavelength is inversely proportional to frequency: waves with higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths.

Examples of wave-like phenomena are sound waves, light, and water waves. A sound wave is a periodic variation in air pressure, while in light and other electromagnetic radiation the strength of the electric and the magnetic field vary. Water waves are periodic variations in the height of a body of water. In a crystal lattice vibration, atomic positions vary periodically in both lattice position and time.

Wavelength is a measure of the distance between repetitions of a shape feature such as peaks, valleys, or zero-crossings, not a measure of how far any given particle moves. For example, in waves over deep water a particle in the water moves in a circle of the same diameter as the wave height, unrelated to wavelength.

This text uses material from Wikipedia, licensed under CC BY-SA