2002 September 2
In studying the Metric Study NBS SP 345-6 Education July 1971 I find
on page 38 a footnote on the mole which quotes the International
Union of Pure and Applied Chemistry as including the photon in the
list of elementary entities which may be used. The 7th edition of
the SI brochure does not include photon in the list of allowed
entities.
Can anybody tell me why?
In editing SI10 we discussed photon in relation to a proposed unit
Einstein which is a mole of photons. We said we can not have such
a unit because the SI does not allow “a mole of photons”.
Robert Bushnell
