This is a list of recurring cycles. See also Index of wave articles, Time, and Pattern.
Astronomy – Axial precession – CNO cycle – Eclipse cycle – Eclipse – Full moon cycle – Galactic year – Great Year – Lunar phase – Mesoamerican calendars – Metonic cycle – Milankovitch cycles – Mira – Moon – Nutation – Orbit – Orbital period – Saros cycle – Sothic cycle – Secularity – Sidereal year – Sunspot – Tide – Tropical year – Year
Animal migration – Avalanche – Carbon cycle – Climate change – Climate change and agriculture – Climate model – Climate oscillation – Clock of the Long Now – Ecology – El Niño/La Niña – Endometrium – Environmental geography – Global cooling – Global warming – Historical temperature record – Hydrogen cycle – Ice age – Transhumance – Milankovitch cycles – Monsoon – Pleistocene – Season – Sulfur cycle – Sunspot – Tide – Timeline of meteorology – 1500-year climate cycle
Age of the Earth – Aluminum cycle – Arsenic cycle – Boron cycle – Bromine cycle – Cadmium cycle – Calcium cycle – Carbonate–silicate cycle – Chlorine cycle – Chromium cycle – Climate change – Copper cycle – Cycle of erosion – Dynamic topography – Dynamic topography – Earthquake cycle – Fluorine cycle – Glaciation – Gold cycle – Iodine cycle – Iron cycle – Lead cycle – Lithium cycle – Manganese cycle – Mass extinction cycles – Mercury cycle – Methane cycle – Ozone–oxygen cycle – Phosphorus cycle – Selenium cycle – Silica cycle – Supercontinent cycle – Vanadium cycle – Wilson cycle – Zinc cycle
Agricultural cycle – Carbon cycle – Crop rotation – Fertile Crescent – Harvest – Nitrogen cycle – Organic farming – Phosphorus cycle – Season – Sulfur cycle – Soil degradation – Sustainable industries – Water cycle
Alternation of generations – Beta oxidation – Bioelectricity – Biological pest control – Biological rhythm – Bipolar disorder – Cardiopulmonary resuscitation – Calvin–Benson cycle – Cell cycle – Chronobiology – Citric acid cycle – Circadian rhythm – Clinical depression – Digestion – Ecology – Feedback – Infradian rhythm - Life cycle – List of biochemistry topics – Marine biology – Menstrual cycle – Neurofeedback – Non-Hodgkin lymphoma – Organic farming – Periodical cicadas – Polymerase chain reaction – Soil degradation – Stomach cancer – Triage – Ultradian rhythm - Urea cycle – Zygote
Bioelectricity – Circadian rhythm – Consciousness – Electroencephalography – Neurofeedback – Persistent vegetative state – Sjögren's syndrome – Sleep - Ultradian rhythm
Cyclic process – Carnot cycle – Double-slit experiment – Dynamic theory of gravity – Physics of music – Resonance – Sonoluminescence – Speed of light – Sunspot
Almost periodic function – Amplitude modulation – Amplitude – Beat – Chaos theory – Cyclic group – Diffraction – Doppler effect – Eigenstate – Eigenvalue – Fibonacci sequence – Fourier series – Frequency domain – Frequency spectrum – Hamiltonian (quantum mechanics) – Harmonic oscillator – Huygens–Fresnel principle – Longitudinal wave – Mechanical wave – Navier–Stokes equations – Partial differential equation – Periodic function – Permutation – Phase (waves) – Physics of music – Power spectrum – Signal – Sine wave – Spectrum of an operator – Translational symmetry – Transverse wave – Wave equation – Wave–particle duality – Wave – Waveform
Absorption spectroscopy – Anders Jonas Ångström – Astronomical spectroscopy – Astronomy – Black body – Blazar – Bremsstrahlung – Caesium – Cherenkov radiation – Color – Diffraction – Digital signal processing – Direct-sequence spread spectrum – Dispersion (optics) – Eigenstate – Eigenvalue – Electromagnetic radiation – Electromagnetic spectroscopy – Electromagnetic spectrum – Electromagnetism – Emission line – Emission spectrum – FM broadcasting – Frequency domain – Frequency hopping – Frequency spectrum – Gamma-ray burst – Hamiltonian (quantum mechanics) – History of radio – Hue – Isotope – Light – Optical brightener – Particle in a spherically symmetric potential – Piezoelectricity – Power spectrum – RADAR – Radio frequency – Radio – Radiocommunications Agency – Redshift – SETI – Spectrogram – Spectrometer – Spectroscopy – Spectrum analyzer – Sunyaev–Zel'dovich effect – Supernova – Telecommunication – Timbre – Very high frequency – Visible light – Visible spectrum – White noise
Acoustic theory – Acoustics – Aerodynamics – Amplitude – Anemometer – Audio feedback – Beat (acoustics) – Bugging – Cherenkov radiation – Cold fusion – Compressibility – Delay-line memory – Diffraction – Doppler effect – Echo sounding – Electronic filter – FTIR – Krakatoa – Loudspeaker – Mach number – Microphone – Ossicles – Pan pipes – Parabolic microphone – Phonetics – Phonon – Piezoelectricity – Psychoacoustics – Sawtooth wave – Shock wave – SID – Sonar – Sonic boom – Sonoluminescence – Soundproofing – Sound recording – Sound – Speech processing – Speed of sound – Sperm whale – Square wave – Subsonic – Subtractive synthesis – Synthesizer – Telephone – Transmission line – Triangle wave – Wave drag – Waveform
Business cycle – Inflation / Recession – Monetary policy – Virtuous circle and vicious circle – Kitchin cycle – Juglar cycle – Kuznets swing
Harmonics – Interval cycle – Musica universalis – Music theory – Physics of music – Ring cycle – Rhythm – Song cycle
Election Cycle – Campaign Cycle – Cycle between political extremes – American political cycle
Astrology – Mantra – Numerology – Pratītyasamutpāda – Samhain – Sexagenary cycle – Surya
Dynastic cycle – Kondratiev wave – Social cycle theory – Tytler cycle
In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. Types of EMR include radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays, all of which are part of the electromagnetic spectrum.
The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band. From low to high frequency these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. The electromagnetic waves in each of these bands have different characteristics, such as how they are produced, how they interact with matter, and their practical applications.
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 terahertz, between the infrared and the ultraviolet.
Spectroscopy is the field of study that measures and interprets electromagnetic spectra. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum.
Spontaneous emission is the process in which a quantum mechanical system transits from an excited energy state to a lower energy state and emits a quantized amount of energy in the form of a photon. Spontaneous emission is ultimately responsible for most of the light we see all around us; it is so ubiquitous that there are many names given to what is essentially the same process. If atoms are excited by some means other than heating, the spontaneous emission is called luminescence. For example, fireflies are luminescent. And there are different forms of luminescence depending on how excited atoms are produced. If the excitation is effected by the absorption of radiation the spontaneous emission is called fluorescence. Sometimes molecules have a metastable level and continue to fluoresce long after the exciting radiation is turned off; this is called phosphorescence. Figurines that glow in the dark are phosphorescent. Lasers start via spontaneous emission, then during continuous operation work by stimulated emission.
In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, troughs, or zero crossings. Wavelength is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. The inverse of the wavelength is called the spatial frequency. Wavelength is commonly designated by the Greek letter lambda (λ). 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.
In physics, mathematics, engineering, and related fields, a wave is a propagating dynamic disturbance of one or more quantities. Periodic waves oscillate repeatedly about an equilibrium (resting) value at some frequency. When the entire waveform moves in one direction, it is said to be a traveling wave; by contrast, a pair of superimposed periodic waves traveling in opposite directions makes a standing wave. In a standing wave, the amplitude of vibration has nulls at some positions where the wave amplitude appears smaller or even zero. Waves are often described by a wave equation or a one-way wave equation for single wave propagation in a defined direction.
Atomic, molecular, and optical physics (AMO) is the study of matter–matter and light–matter interactions, at the scale of one or a few atoms and energy scales around several electron volts. The three areas are closely interrelated. AMO theory includes classical, semi-classical and quantum treatments. Typically, the theory and applications of emission, absorption, scattering of electromagnetic radiation (light) from excited atoms and molecules, analysis of spectroscopy, generation of lasers and masers, and the optical properties of matter in general, fall into these categories.
A quantum mechanical system or particle that is bound—that is, confined spatially—can only take on certain discrete values of energy, called energy levels. This contrasts with classical particles, which can have any amount of energy. The term is commonly used for the energy levels of the electrons in atoms, ions, or molecules, which are bound by the electric field of the nucleus, but can also refer to energy levels of nuclei or vibrational or rotational energy levels in molecules. The energy spectrum of a system with such discrete energy levels is said to be quantized.
Quantum superposition is a fundamental principle of quantum mechanics that states that linear combinations of solutions to the Schrödinger equation are also solutions of the Schrödinger equation. This follows from the fact that the Schrödinger equation is a linear differential equation in time and position. More precisely, the state of a system is given by a linear combination of all the eigenfunctions of the Schrödinger equation governing that system.
Radio waves are a type of electromagnetic radiation with the lowest frequencies and the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz (GHz) and below. At 300 GHz, the corresponding wavelength is 1mm, which is shorter than the diameter of a grain of rice. At 30 Hz the corresponding wavelength is ~10,000 kilometers, which is longer than the radius of the Earth. Wavelength of a radio wave is inversely proportional to its frequency, because its velocity is constant. Like all electromagnetic waves, radio waves in a vacuum travel at the speed of light, and in the Earth's atmosphere at a slightly slower speed. Radio waves are generated by charged particles undergoing acceleration, such as time-varying electric currents. Naturally occurring radio waves are emitted by lightning and astronomical objects, and are part of the blackbody radiation emitted by all warm objects.
Scattering is a term used in physics to describe a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities in the medium through which they pass. In conventional use, this also includes deviation of reflected radiation from the angle predicted by the law of reflection. Reflections of radiation that undergo scattering are often called diffuse reflections and unscattered reflections are called specular (mirror-like) reflections. Originally, the term was confined to light scattering. As more "ray"-like phenomena were discovered, the idea of scattering was extended to them, so that William Herschel could refer to the scattering of "heat rays" in 1800. John Tyndall, a pioneer in light scattering research, noted the connection between light scattering and acoustic scattering in the 1870s. Near the end of the 19th century, the scattering of cathode rays and X-rays was observed and discussed. With the discovery of subatomic particles and the development of quantum theory in the 20th century, the sense of the term became broader as it was recognized that the same mathematical frameworks used in light scattering could be applied to many other phenomena.
In the physical sciences, the wavenumber, also known as repetency, is the spatial frequency of a wave, measured in cycles per unit distance or radians per unit distance. It is analogous to temporal frequency, which is defined as the number of wave cycles per unit time or radians per unit time.
A sine wave, sinusoidal wave, or sinusoid is a periodic wave whose waveform (shape) is the trigonometric sine function. In mechanics, as a linear motion over time, this is simple harmonic motion; as rotation, it corresponds to uniform circular motion. Sine waves occur often in physics, including wind waves, sound waves, and light waves, such as monochromatic radiation. In engineering, signal processing, and mathematics, Fourier analysis decomposes general functions into a sum of sine waves of various frequencies, relative phases, and magnitudes.
In mathematics, physics, electronics, control systems engineering, and statistics, the frequency domain refers to the analysis of mathematical functions or signals with respect to frequency, rather than time, as in time series. Put simply, a time-domain graph shows how a signal changes over time, whereas a frequency-domain graph shows how the signal is distributed within different frequency bands over a range of frequencies. A complex valued frequency-domain representation consists of both the magnitude and the phase of a set of sinusoids at the frequency components of the signal. Although it is common to refer to the magnitude portion as the frequency response of a signal, the phase portion is required to uniquely define the signal.
A normal mode of a dynamical system is a pattern of motion in which all parts of the system move sinusoidally with the same frequency and with a fixed phase relation. The free motion described by the normal modes takes place at fixed frequencies. These fixed frequencies of the normal modes of a system are known as its natural frequencies or resonant frequencies. A physical object, such as a building, bridge, or molecule, has a set of normal modes and their natural frequencies that depend on its structure, materials and boundary conditions.
This is a glossary for the terminology often encountered in undergraduate quantum mechanics courses.
In vibrational spectroscopy, an overtone band is the spectral band that occurs in a vibrational spectrum of a molecule when the molecule makes a transition from the ground state (v=0) to the second excited state (v=2), where v is the vibrational quantum number obtained from solving the Schrödinger equation for the molecule.
The index of physics articles is split into multiple pages due to its size.
In the physical sciences, the term spectrum was introduced first into optics by Isaac Newton in the 17th century, referring to the range of colors observed when white light was dispersed through a prism. Soon the term referred to a plot of light intensity or power as a function of frequency or wavelength, also known as a spectral density plot.