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# Intensity Formula - What's k? watch

1. I = (k * I nought)/x^2

Is k = Pi/4?

Cheers
2. 1/(4*pi) ?
It's just a constant in the "intensity is inversely proportional to distance squared" thing.
For a point source the energy spreads out over an area 4*pi*x² so intensity at distance x is:
I = P / 4*pi*x² (where P is the power of the source)."

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