On Dec 28, 1:38*am, Cecil Moore wrote:
Keith Dysart wrote:
Perhaps try googling "in the limit as t approaches 0..."

So how many joules can pass a point in zero seconds?

You have descended into silliness. You are out on your
Harley doing 60 miles/hour. How far do you travel in 0
seconds?

So your point was?

But at least you now see the utility.

Nope, I don't. I don't think the concept of instantaneous
power is mentioned at all in "Optics", by Hecht.

Ahhh. The difficulty is because you don't "think" that
the concept is mentioned in Hecht. Could that be because
at 5E14 Hz, it is difficult to measure? Try a circuit
analysis or transmission line book. You will have more
luck. There is a good chance that your Ramo and Whinery
mention it. Look near where they derive
Pavg = Vrms * Irms * cos(theta)

...Keith