ANDREW BROOKES, NATIONAL PHYSICAL LABORATORY / SCIENCE PHOTO LIBRARY ANDREW BROOKES, NATIONAL PHYSICAL LABORATORY / SCIENCE PHOTO LIBRARY
Measuring light intensity. Scientist using a cryogenic radiometer to measure light intensity. The cryogenic radiometer is an instrument that precisely measures the standard unit for luminous intensity, the candela. It does this by measuring the power of an intensity stabilised laser beam at cryogenic (sub-zero) temperatures inside a vacuum. Photographed at the National Physical Laboratory in Teddington, UK.
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