[Laser] Spherical geometery

[laser@mailman.qth.net]

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