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NOTES
The amount of radiant heat received from an emitter reduces with the square of the distance from the emitter.
When the distance is doubled - the received radiant heat is ¼ what it had been.
When the distance is tripled - the received radiant heat is 1/9th what it had been.
Click Animation
The inverse is true too, cut the distance to 1/3 and receive 9X the radiant heat - this is important to remember as radiant heat can increase quickly as when approaching the source.