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). One microflick is equivalent to 10 kilowatts per steradian per cubic meter (kW·sr−1·m−3).
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. While it started out used only in Lockheed, many in the radio astronomy field adopted its use.
- 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.
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- Schlessinger (1994). Infrared Technology Fundamentals, 2nd ed. CRC Press. p. 21. ISBN 9780824792596.