Where Does the Power Go?
 

Cecil Moore wrote:
Gene Fuller wrote:

Don't bother. I understand the physics quite well, thank you.


So, is anything technically wrong with what I posted?
It is all copied out of various parts of "Optics", by
Hecht.

From what page in "Optics" by Hecht is the 1 watt laser problem and
analysis copied?

73, Jim AC6XG

Where Does the Power Go?
 

Jim Kelley wrote:
From what page in "Optics" by Hecht is the 1 watt laser problem and
analysis copied?

The 1 watt laser mental exercise is my idea. Everything
else is directly from "Optics", by Hecht.

A 1 watt ideal laser was chosen for its single frequency
and coherent characteristics to avoid any more "brighter
than the surface of the sun" postings.

Why are you afraid to discuss a 1 watt laser?
--
73, Cecil http://www.w5dxp.com

Where Does the Power Go?
 

Jim Kelley wrote:
Not exactly as per Hecht. Note to the casual reader: please be advised
that unlike Cecil, Eugene Hecht does not claim that power is equal to
irradiance.

Here's a quote from "Optics", by Hecht concerning irradiance.
"... since the *power* cannot be measured instantaneously, the
detector must integrate the energy flux over some finite time,
T. ... The time-averaged value of the Poynting vector, ..., is
a measure of I." - where I is the irradiance and the Poynting
vector is the power flow vector.

Hecht seems to treat irradiance the same way that RF engineers
treat power flow vectors. Hecht also says that integrating energy
flux over some finite time is a measure of power. Presumably,
that could be a non-destructive mental integration.

In "Optics", the definition of irradiance is: "the average energy
per unit area per unit time". That's the same definition as the
power flow vector from the IEEE Dictionary: "... *power* per
unit-area propagating in the wave".

Also from the IEEE Dictionary: "Poynting vector - ... The integral
of P(t,r) over a surface is the instantaneous electromagnetic
*power flow* through the surface."

Do you really think Hecht used the Poynting vector while ignorant
of its definition?

When an astronomer draws a spherical boundary around the sun and
calculates the power output of the sun, most of that power is
heading out to empty space and doing no work. Maybe you should
campaign to have that calculation removed from publication.
--
73, Cecil http://www.w5dxp.com

Where Does the Power Go?
 

Cecil Moore wrote:
Gene Fuller wrote:
Don't bother. I understand the physics quite well, thank you.

So, is anything technically wrong with what I posted?
It is all copied out of various parts of "Optics", by
Hecht.

Cecil,

Yes, there was something technically wrong. The message I responded to
had a glaring violation of conservation of energy. Your follow-up
corrected the problem.

73,
Gene
W4SZ

Where Does the Power Go?
 

Cecil Moore wrote:
Richard Clark wrote:
And electric and magnetic fields exist quite independently of ANY
photons (invisible or otherwise) ...

Richard, I suggest you take time to digest the material before making
any more obviously false statements like the above.
--
73, Cecil, w5dxp.com
Cecil,
Looked at your site.Love your bike.73
Bill KC9IRR

Where Does the Power Go?
 

sapper wrote:
Looked at your site. Love your bike.
73, Bill KC9IRR

Just put 1500 miles on it over the long
weekend. My sister asked: "What if it's
a bad day?" (weather-wise)

Told her any day on a Harley is a good day
and if I died on it, I would die happy.
--
73, Cecil http://www.w5dxp.com

Where Does the Power Go?
 

Gene Fuller wrote:
Yes, there was something technically wrong. The message I responded to
had a glaring violation of conservation of energy. Your follow-up
corrected the problem.

Gene, as you know, there is no such thing as a violation of
conservation of energy. But the reflectance at the thin-film
surface is 0.01 and a reflection is unavoidable. So how does
the reflected 0.01 watts/unit-area of irradiance keep from
violating the conservation of energy principle? Where does
that energy go? My follow-up answered those questions. Two
rearward pointing power flow vectors are associated with
wave cancellation of the EM fields. That's destructive
interference resulting in constructive interference in the
opposite direction.
--
73, Cecil http://www.w5dxp.com