[Laser] Spherical geometery

Mon, 16 Sep 2002 11:34:30 -0400 (EDT)

	Dear Group,

	The effects and properties of coherent light of one narrow
frequency which is highly directed and non coherent which is mixed
wavelengths and non directed are not comparable.
	Call the two parameters A and B.

	Education in bits and pieces and guesses as to what someone wants
to know, why they want to know and what use the information will be put to
will probably not be as effective as a clear overview.   

	If you wish to understand the differences between the two you will
be far better off to begin with a reasonably good general text such as The
McGraw Hill Encyclopedia of Science and Technology ... THE PAPER TEXT in
the library.  Look up the topic[s] such as light and laser and follow and
read the suggested tpics in the balance of the encyclopedia.  If you run
across a term you cannot honestly explain to a 12 year old of any
nationality or gender then look it up too.

	Go to societies on the topic.

	If helps to keep something I call:

	The book of what.   It is a simple series of reminders in your own
hand and-or in your own words or selected  text and-or diagrams from
others.  When you see a good tutorial or quick overview or definition
anywhere then copy it and don't tear it out of a a magazine or book.  The
very proceedure  of copying even on a photocpoier helps you to remember
the information.  Be sure you make note of where the information came
from.

On Mon, 16 Sep 2002, Stelios Passas wrote:

> Why you want this? It is simpler.
> Since the bulb is a nearly isotropic source, it radiates all its power
> "uniformly" in a sphere. The area of the pupil of your eye catches a part of
> this energy.
> Calculate what percentage is the area of your eye-pupil to the area of a
> sphere with radius the distance between you and the bulb. That will give you
> how much of the radiated power enters your eye.
> Stelios Passas
> 
> ----- Original Message -----
> From: <[email protected]>
> To: <[email protected]>
> Cc: <[email protected]>
> Sent: Monday, September 16, 2002 3:12 PM
> Subject: [Laser] Spherical geometery
> 
> 
> Hi.
> 
> A week ago someone asked me what would the equivalent output power of a
> light
> bulb be when compared to my 5mW Laser when the bulb and laser were viewed at
> a distance.
> 
> Having rehashed the question a little, the member of my amateur radio club
> was trying to find out the power of a normal household filament bulb ( near
> isotropic source) which would appear as bright as my 670nm laser at a
> distance.
> 
> Ignoring, for the moment, the different eye sensitivities to wavelength, I
> have tried without success to find a formula relating the divergence of a
> laser to the area of a sphere. I hope to use it to calculate the percentage
> area illuminated and hence make a comparision between filament bulb and
> laser.
> 
> So, my question: Does anyone on the list have a formula which relates
> divergence in milli-radians to the area of a sphere?
> 
> (In future I'll just say "no idea" )
> 
> 
> 
> 73
> 
> David  G0MRF
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