Talk:Femtosecond

Untitled
I think there is a mis calculation of the femto second in Wikipedia. A femto second to a second, is a second to 31,709,791 years. This need to be corrected

69.248.168.62 (talk) 20:58, 21 August 2009 (UTC)

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Calculation of wavelength of light
It should be noted that the calculation to determine the wavelength of visible light is only useful in media with a relative permittivity (refraxtive index^2) of 1 (being a vacuum, and very closely air). If the media were different in relative permittivity (refractive index^2) i.e. glass, this calculation wouldn't be correct.

I suggest that: This time can be calculated by dividing the wavelength of the light by the speed of light (approximately 3 x 108 m/s) to determine the time required for light to travel that distance. 1.3 femtoseconds (fs) – cycle time for 390 nanometre light, at the transition between violet visible light and ultraviolet 2.57 femtoseconds – cycle time for 770 nanometre light, at the transition between red visible light and near-infrared be changed to: This time can be calculated by dividing the wavelength of the light in a vacuum by the speed of light in the same media (approximately 3 x 108 m/s) to determine the time required for light to travel that distance. 1.3 femtoseconds (fs) – cycle time for 390 nanometre light in a vacuum/air, at the transition between violet visible light and ultraviolet 2.57 femtoseconds – cycle time for 770 nanometre light in a vacuum/air, at the transition between red visible light and near-infrared Or something along these lines. MrLaister —Preceding unsigned comment added by 81.111.49.34 (talk) 00:13, 26 January 2010 (UTC)

Unsourced conversion seems wrong
The article states "One femtosecond is the amount of time that it takes light to travel approximately 3 feet. My source of this info is unknown." According to my calculations, assuming c = 299,792,458 m/s, and that one femtosecond is 10^-15 second, then (10^-15)*c equals the distance light would travel in one femtosecond. Unit analysis shows this to be correct as (m/s)*s=m. Simplifying the statement gives the answer: 0.000000299792458 meters. Or, in scientific parlance: 2.99792458*10^-7 meters. Conversion to feet is trivial, and I used OnlineConversion for this task: about 9.83*10^-7 feet (or about 0.00001 inch) - note that is is dramatically different than the unsourced statement above, and so I'm removing said statement. KF6KJG (talk) 17:43, 27 October 2010 (UTC)

Etymology
The femto- prefix comes from the Swedish word for 'fifteen'.Mygodlesslife (talk) 21:47, 19 February 2011 (UTC) mygodlesslife

J'ai une question
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