# 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 10^{10} 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]

## History

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.

## References

- 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.
- Rowlett, Russ. "How Many? A Dictionary of Units of Measurement". Retrieved 10 August 2012.
- Schlessinger (1994).
*Infrared Technology Fundamentals, 2nd ed*. CRC Press. p. 21. ISBN 9780824792596.