Astrophysics (index)

Frequency

(number of cycles per unit of time, such as waves per second)

Frequency is number of cycles per unit time, e.g., per second. Typical measurement is in Hertz, number of cycles per second. In astrophysics, frequency is used for Electromagnetic Radiation (EMR), in which the Wavelength times the frequency is the speed of Electromagnetic (EM) waves. The energy of a photon is directly related to the frequency of the the electromagnetic radiation:

E = h × f

Wavelength is often used to characterize electromagnetic radiation, perhaps frequency often being most used for the longest wavelengths (e.g., Radio) and photon energy most often used for the shortest (e.g., Gamma Rays).

Other astronomical phenomena such as regularly pulsing radiation (Pulsar (PSR), spinning Neutron Star) can have a frequency, i.e., number of cycles per some unit of time.


(EMR,measure)
http://en.wikipedia.org/wiki/Frequency

Referenced by:
Absorption Line
AB System
Atacama Cosmology Telescope (ACT)
Anisotropy
Antenna Temperature
Black-Body Radiation
Bohr Model
Bolometer
Cambridge Catalog of Radio Sources
Canadian Hydrogen Intensity Mapping Experiment (CHIME)
Chirp
Carbon Monoxide (CO)
Coherent Light
Compton Scattering
Corotation Resonance (CR)
Cyclotron Radiation
Degeneracy
Velocity Dispersion (σ)
Doppler Shift
Eigenmode
Electron Orbital
Extremely Low Frequency (ELF)
Epicyclic Frequency
Frequency Modulation (FM)
Fourier Space
Fourier Transform
Fast Radio Burst (FRB)
Galactic Electron Density
Galaxy Power Spectrum
Gamma Rays
Green Bank Telescope (GBT)
Gravitational Wave (GW)
Habitable Zone (HZ)
Hadley Cell
Infrared (IR)
Infrared Survey Facility (IRSF)
Jansky (Jy)
Lunar Reconnaissance Orbiter (LRO)
Crab Nebula (M1)
Nanohertz Gravitational Waves
Passband
Phased Array
Photoionization
Parkes Catalog (PKS)
Planck
Planck Constant (h)
Plasma Frequency
Power Law
Pulsar (PSR)
Radiance
Radiant Flux
Radio
Radio Astronomy
Red Noise
Radio Frequency Interference (RFI)
Rossby Number (Ro)
Equation of Radiative Transfer (RTE)
Spectral Energy Distribution (SED)
Sensitivity Function (S)
Square Kilometre Array (SKA)
Super Low Frequency (SLF)
Solar and Heliospheric Observatory (SOHO)
Spectral Power Distribution (SPD)
Spectral Density
Spectral Index (α)
South Pole Telescope (SPT)
Synchrotron Self-Compton (SSC)
Subradio
Sunyaev-Zel'dovich Effect (SZ Effect)
Thomson Scattering
Time Series Analysis
Tremendously Low Frequency (TLF)
Ultra Low Frequency (ULF)
Virgo
Very Low Frequency (VLF)
Wavelength
Atmospheric Window
X-ray

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