Recently physicists have managed to build "attosecond lasers", lasers which emit pulses 10^-18 seconds long, interrupted by much longer periods of darkness (at least 10^-14 seconds). Before them, lasers emitting femtosecond (10^-15 seconds) pulses have been around. Assuming they produce visible light, what colour is it?

Your calculation will come in useful, but it is not quite the solution.  The pulses are not exactly rectangular, so their nominal width can well contain only partial wavelengths.  And I didn't say anything about the light being monochromatic.

Posted by vswitchs on 2006-10-06 14:41:05