Answer:
I₂ = 8 mG
Explanation:
The intensity of a beam is
I = P / A
Where P is the emitted power which is 3) 3
Let's use index 1 for the initial position of r₁ = 6 ft and 2 for the second position r₂ = 3 ft
I₁ A₁ = I₂ A₂
I₂ = I₁ A₁ / A₂
The area of the beam if we assume that it is distributed either in the form of a sphere is
A₁ = 4π r²
We substitute
I₂ = I₁ (r₁ / r₂)²
I₂ = 2 (6/3)²
I₂ = 2 4
I₂ = 8 mG
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