# Flick (physics)

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This article is about the unit of spectral radiance. For the unit of time, see [Flick (time)](/source/Flick_(time)).

In [optical engineering](/source/Optical_engineering) and [telecommunications engineering](/source/Telecommunications_engineering), the **flick** is a unit of [spectral radiance](/source/Spectral_radiance). One flick corresponds to a spectral radiance of 1 [watt](/source/Watt) per [steradian](/source/Steradian) per square [centimeter](/source/Centimeter) of surface per [micrometer](/source/Micrometre) of span in wavelength (W·sr−1·cm−2·μm−1). This is equivalent to 1010 [watts](/source/Watt) per [steradian](/source/Steradian) per cubic [meter](/source/Meter) (W·sr−1·m−3). In practice, spectral radiance is typically measured in microflicks (10−6 flicks).[1] One microflick is equivalent to 10 kilowatts per steradian per cubic meter (kW·sr−1·m−3).[2]

## History

In [radio astronomy](/source/Radio_astronomy), the unit **flik** was coined by a group at [Lockheed](/source/Lockheed_Corporation) in [Palo Alto, California](/source/Palo_Alto,_California) as a substitute for the [SI derived unit](/source/SI_derived_unit) W cm−2 sr−1 μm−1, or watts divided by [centimeters](/source/Centimeters) squared, steradians, and [micrometers](/source/Micrometre).[3] While originally used only at Lockheed, many in the radio astronomy field adopted its use.

## References

1. Palmer, James M. ["The SI system and SI units for Radiometry and photometry"](https://web.archive.org/web/20120802170633/http://www.optics.arizona.edu/palmer/opti400/suppdocs/bkappndx.pdf). Archived from [the original](http://www.optics.arizona.edu/palmer/opti400/suppdocs/bkappndx.pdf) on 2012-08-02. Retrieved 2012-08-10.

1. Rowlett, Russ. ["How Many? A Dictionary of Units of Measurement"](http://www.unc.edu/~rowlett/units/dictF.html#flick). [Archived](https://web.archive.org/web/20120920072819/https://www.unc.edu/~rowlett/units/dictF.html#flick) 20 September 2012 at the Wayback Machine. Retrieved 10 August 2012.

1. Schlessinger (1994). [*Infrared Technology Fundamentals, 2nd ed*](https://books.google.com/books?id=QPBQ5w4X8RkC&q=flik+unit+astronomy&pg=PA21). [CRC Press](/source/CRC_Press). p. 21. ISBN 9780824792596.

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Adapted from the Wikipedia article [Flick (physics)](https://en.wikipedia.org/wiki/Flick_(physics)) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Flick_(physics)?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.