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Fundamental Principles of Engineering Nanometrology, 2nd Edition
book

Fundamental Principles of Engineering Nanometrology, 2nd Edition

by Richard Leach
May 2014
Intermediate to advanced content levelIntermediate to advanced
384 pages
11h 58m
English
William Andrew
Content preview from Fundamental Principles of Engineering Nanometrology, 2nd Edition
Appendix A

SI Units of Measurement and Their Realisation at NPL

Quantity Unit (Symbol) Definition Realisation
Time second (s) The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom. The second is realised by primary caesium frequency standards to about 2 parts in 1015. The majority are traditional caesium-beam designs, but the latest use lasers to control and detect the atoms.
Length metre (m) The metre is the length of the path travelled by light in a vacuum during a time interval of 1/299 792 458 of a second. At NPL, the metre is currently realised through the wavelength of the 633 nm radiation from an iodine-stabilised ...
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Publisher Resources

ISBN: 9781455777532