I am a little late to explain what those numbers do as
Lloyd and others have explained them well, but an interesting
comment is that the energy in a half-wave-rectified sine wave is
.707 that of a RMS sign wave. A cheap and dirty light dimmer can
be found in some appliances that consists of nothing more than a
diode in series with the light bulb and a switch across the
diode. When the switch is closed, you get the full sine wave and
the bulb runs on pure AC. When the switch is opened, the bulb is
actually running on pulsating DC and the end result is that it
dims slightly as it is running on .707 of the energy of the full
sine wave.

	The trouble with all that is that there is a noticeable
visual flicker to the light at 60 HZ and probably even a little
more at 50 HZ as one would find outside the United States and
Canada.

	Back when I was a technician with OSU's Audio Visual
Center, there was a line of overhead projectors whose lamps, for
some odd reason, always ran in series with a diode.
Occasionally, the diode went bad and shorted. The lamps which
were very expensive, tended to burn out quickly as they were now
running at a higher voltage than they should.

	The angry customers would say that they had replaced X
number of bulbs in X number of days and they kept on blowing
out.

	We would check the diode, find it shorted and stick in a
new one along with a new lamp and they were good to go once
again.

	I used to joke that it was a conspiracy between the
design engineers and the light bulb makers. You put a dodgy
diode in that blows occasionally, and we get to sell a lot more
bulbs.

	Martin

Lloyd Rasmussen writes:
> Also, .707... is the sine and also the cosine of 45 degrees, and is 1 over
> the square root of 2.  The number 1.4142136... is the square root of 2.  
> The
> elipses in these numbers indicate that there are infinitely more decimal
> digits; these are called irrational numbers because they are not the ratio
> of any whole numbers.
> 73 -- Lloyd, W3IUU