Beeld:Platinum-Iridium meter bar.jpg
vanuit Wikipedia, die vrye ensiklopedie.
No higher resolution available.
Platinum-Iridium_meter_bar.jpg (270 × 175 pixel, file size: 21 KB, MIME type: image/jpeg)
International Prototype Metre standard bar made of platinum-iridium. This was the standard until 1960, when the new SI system used a krypton-spectrum measurement as the base. In 1983 the current metre was defined by a relationship to the speed of light in a vaccuum. (NIST)
http://www.mel.nist.gov/div821/webdocs-14/lsi_2.htm
 |
This image is in the public domain because it contains materials that originally came from the National Institute of Standards and Technology. |
 |
Prentskakels
Die volgende bladsye gebruik hierdie prent:
