Always on the lookout for better ways to measure all kinds of things, researchers at the National Institute of Standards and Technology (NIST) have published a detailed study suggesting an “elegant” improved definition for the standard unit of light power, the optical watt.
But it’s more than just an opportunity to nerd out over an international measurement unit. The proposed definition promises a more precise, less expensive and more portable method for measuring this important quantity for science, technology, manufacturing, commerce and national defense.
Instead of the current definition based on comparisons to electrical heating, the NIST study suggests the optical watt could be determined from light’s radiation force and its speed, a fundamental constant. Fundamental constants are numbers that stay the same all over the world, making measurements based on them universal. Primary standards that define measurement units based on fundamental constants are considered ideal.
“Johannes Kepler made the first observations of radiation pressure in the early 17th century,” NIST project leader John Lehman said. “A few years ago, we decided to create a primary measurement standard on this basis.” Maybe someday we will all redefine optical power this way.”
The proposed definition is based on James Clerk Maxwell’s work in 1862 showing that the force exerted by light is proportional to its power divided by the speed of light. Now, practical measurement standards can be created on this basis thanks to recent NIST technical advances.
The NIST proposal is in sync with the recent study suggests universal method measuring light power
