Flick (physics)

In optical engineering and telecommunications engineering, the flick is a unit of spectral radiance. One flick corresponds to a spectral radiance of 1 watt per steradian per square centimeter of surface per micrometer of span in wavelength (W·sr−1·cm−2·μm−1). This is equivalent to 1010 watts per steradian per cubic 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]


In radio astronomy, the unit flik was coined by a group at Lockheed in Palo Alto, California as a substitute for the SI derived unit W cm−2 sr−1 µm−1, or watts divided by centimeters squared, steradians, and micrometers.[3] While it started out used only in Lockheed, many in the radio astronomy field adopted its use.


  1. Palmer, James M. "The SI system and SI units for Radiometry and photometry" (PDF). Archived from the original (PDF) on 2012-08-02. Retrieved 2012-08-10.
  2. Rowlett, Russ. "How Many? A Dictionary of Units of Measurement". Retrieved 10 August 2012.
  3. Schlessinger (1994). Infrared Technology Fundamentals, 2nd ed. CRC Press. p. 21. ISBN 9780824792596.

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