From the Editor

Let us interrupt the discussion of our correspondence to con-sider some matters of terminology in optics. In the June 1962 issue of Physics Today the report of the SUN (Symbols, Units, and Nomenclature) Commission of the IUPAP was presented in some detail. Many people who hastily read this concluded that the section on optics is now gospel and that their papers must conform to this new nomenclature. This is not quite true: the report was a provisional or preliminary set of recommenda-tions, and it has not yet been adopted by the American Institute of Physics. This AIP adoption must in turn be preceded by approval of the Member Societies, and we of the Optical Society have a particular interest in the sections pertaining to optics. On certain matters which seem properly editorial your Editors have already acted without formal instruction from the Society; for example, all of the editors of the journals of the AIP or its Member Societies voted to accept the SUN Commission recom-mendation that units named in honor of scientists shall be rep-resented by the name in lower case, but with its symbol or ab-breviation capitalized. Thus the unit of inductance is the henry and its symbol is H, the unit of magnetic intensity is the oersted and its symbol Oe. In English a proper name has really arrived when we accept it into the language uncapitalized: braille, cereal, pasteurize, mesmerize, macadamize, vulcanize, diesel, saxophone. The expression of units derived from proper names

218 APPLIED OPTICS / Vol. 2, No. 2 / February 1963

in lower case is not new, this has been AIP Style Manual etiquette for many years. What is new and perhaps controversial to us is the capitalization of the symbol. Some have asked why should joule and watt be so honored when erg and dyne are not? On some the spelling is even altered, such as decibel, dB and ohm, Ω. And what should we do about mho and daraf? The Swedes then argued that their letter Å is not the same as A, and comes in fact at the end of their alphabet (after z and before ä and ö). We have therefore agreed to reinsert the diacritical mark on the symbol Å, although the unit remains the angstrom. This is a slight variant from the SUN report, which recommended ångström for the unit.

At a meeting of the AIP Publications Board about a year ago the editors discussed this proposal to capitalize symbols of units which derive from proper names and decided to adopt this system as of July 1962. This is purely an editorial convention, already agreeable to most of the other member countries of the SUN Commission; the only objections were the minor quibbles mentioned above. On a more controversial matter, the use of the unit hertz, Hz, for cps, the AIP editors took exception. The present editorial policy of this journal is to accept hertz, Hz, if an author uses it consistently throughout, particularly in our foreign-language articles, but to prefer cps for English-language papers.

A few of our audience have grumbled at this change, but most of us have accepted the new convention philosophically in the interest of international uniformity. One of our authors was so anxious to change his angstroms from A to Å that he changed all his amperes as well.

Let us consider some of the other recommendations of the SUN report. The section which will surely stir up the most argument is section 7.6 (page 25 of the June 1962 Physics Today) where many of the symbols listed as "preferred" differ from those preferred for Applied Optics and J. Opt. Soc. Am. Dr. Judd has discussed our preferred units on the Editor's Page of J. Opt. Soc. Am. for April 1962. In a future column we will discuss some of the differences, and we hope tha t those of you who have opinions on nomenclature will express them to us prior to the vote for adoption of this section of the SUN Commission report.

Although the AIP Publications Board adopted the SUN table of prefixes to represent the various powers of ten, we have taken several exceptions to this. For example, 109 electron volts can be written as either GeV or BeV. The SUN report states that the use of double prefixes should be avoided when single pre-fixes are available. Thus nanometer, nm, is indicated as preferable

to millimicron, mµ. We will continue, at least for the present, to accept millimicrons for the spectroscopic sense of wavelength of light, although nanometer is preferred for non-spectroscopic senses such as the thermal expansion of a rod or the displacement of an interferometer plate. (We do not wish to imply that we encourage the use of mµ; why not express the wavelength in angstroms?) Again, the use of µ to mean the noun "micron" is so widespread that we do not propose to limit µ to mean only the adjectival prefix "micro," so tha t 10 - 6 meter remains 1 µ and not 1 µm (micrometer). The SUN report gives "sr" as the symbol for steradian instead of the commonly used "ster."

Some readers were frightened by the British English used in the SUN report: metre, gramme, litre, dioptre. These spellings would of course be Americanized by the AIP. After this report is adopted, the AIP will issue a revised Style Manual. We will then expect prospective authors to conform to the approved nomenclature.

JOHN N. HOWARD

February 1963 / Vol. 2, No. 2 / APPLIED OPTICS 219