The idiot savant Cecil Moore wrote:

Therefore, those bright rings are just an illusion and
don't contain more than the average energy in the two
superposed waves.

You couldn't be more wrong in your interpretation.

Perhaps you will understand it this way: the bright rings have an
intensity which is equal in energy to the sum of the energy in the two
superposed waves. Energy doesn't have to come from anywhere else to
balance the equation.

The error you're making is the assumption that since the intensities
don't add up, something has to come from somewhere else. But that's a
wrong assumption to make. One shouldn't expect intensity to add like
that. Obviously it doesn't add like that. The fields are what add and
subtract, not intensity (or power). Power is the time derivative of
energy - that's the reason a squared term comes in. But power and
intensity don't propagate, therefore they don't superpose, and
shouldn't be added algebraically. Fields, voltage, current, energy -
it makes sense to sum those things algebraically.

When you double something and then square the sum, you get a factor of
four. But you're still only doubling the 'thing' of interest.
Depositing two paychecks and squaring the sum doesn't make your bank
balance go up by a factor of four. But it is certainly true that you
would have to borrow money from someone to make that happens. The
point is that it's not a realistic expectation.

I assume you know that the meter face on your Bird wattmeter is
calibrated exponentially. So, when your Bird power meter reading goes
up by a factor of four, what do you think the voltage across its meter
movement has actually increased by? The thing is, the Bird company
understands that when power reading quadruples, the circuit voltage
has only doubled. You'll note they don't claim that since the reading
quadrupled instead of doubling, the "extra" power had to come from
somewhere else.

If you can't understand this, that's fine. But it's not an excuse to
get so bloody belligerent with people about it.

ac6xg

Jim Kelley wrote:
The idiot savant Cecil Moore wrote:

Therefore, those bright rings are just an illusion and
don't contain more than the average energy in the two
superposed waves.

You couldn't be more wrong in your interpretation.

Perhaps you will understand it this way: the bright rings have an
intensity which is equal in energy to the sum of the energy in the two
superposed waves. Energy doesn't have to come from anywhere else to
balance the equation.

The error you're making is the assumption that since the intensities
don't add up, something has to come from somewhere else. But that's a
wrong assumption to make. One shouldn't expect intensity to add like
that. Obviously it doesn't add like that. The fields are what add and
subtract, not intensity (or power). Power is the time derivative of
energy - that's the reason a squared term comes in. But power and
intensity don't propagate, therefore they don't superpose, and shouldn't
be added algebraically. Fields, voltage, current, energy - it makes
sense to sum those things algebraically.

When you double something and then square the sum, you get a factor of
four. But you're still only doubling the 'thing' of interest.
Depositing two paychecks and squaring the sum doesn't make your bank
balance go up by a factor of four. But it is certainly true that you
would have to borrow money from someone to make that happens. The point
is that it's not a realistic expectation.

I assume you know that the meter face on your Bird wattmeter is
calibrated exponentially. So, when your Bird power meter reading goes
up by a factor of four, what do you think the voltage across its meter
movement has actually increased by? The thing is, the Bird company
understands that when power reading quadruples, the circuit voltage has
only doubled. You'll note they don't claim that since the reading
quadrupled instead of doubling, the "extra" power had to come from
somewhere else.

If you can't understand this, that's fine. But it's not an excuse to
get so bloody belligerent with people about it.

ac6xg


What! You mean you don't believe in the law of the conservation of
power? Cecil does. Don't tell anyone, but I think he may believe in
the law of the conservation of speed, too.
73,
Tom Donaly, KA6RUH

Tom Donaly wrote:
What! You mean you don't believe in the law of the conservation of
power? Cecil does.

You know that is a lie, Tom. I believe in the conservation of
energy and momentum. I do not believe in any conservation of
power and speed.
--
73, Cecil http://www.w5dxp.com

Jim Kelley wrote:
Perhaps you will understand it this way: the bright rings have an
intensity which is equal in energy to the sum of the energy in the two
superposed waves. Energy doesn't have to come from anywhere else to
balance the equation.

That just shows that you still don't understand the
interference process. The bright rings have an intensity
which is equal in energy to *double* the sum of the energy
in the two superposed waves. If P1 = P2, the total energy
in the bright rings is P1+P2+2*SQRT(P1*P2) = 2*(P1+P2).

That "extra" constructive interference energy has to come
from somewhere and it comes from the dark areas where
destructive interference occurs. In the dark areas,
P1+P2-2*SQRT(P1*P2) = 0. Taking the average of those two
equations yields (P1+P2) which is the sum of the energy
in the two superposed waves. That's only half as bright
as the bright rings.

The constructive interference energy has to exactly equal
the destructive interference energy or else the conservation
of energy principle is violated and, sure enough, they do
equal each other.
--
73, Cecil http://www.w5dxp.com