SOLUTION: Hello, I need help with this problem: The intensity of a light source varies inversely with the square of the distance from the source. Four feet from the source the intensity i

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Question 455228: Hello, I need help with this problem:
The intensity of a light source varies inversely with the square of the distance from the source. Four feet from the source the intensity is 9 foot candles. What is the intensity 3 feet from the source.
Thank you.
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
The intensity of a light source varies inversely with the square of the distance from the source.
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I = k/d^2
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Solve for "k" using "Four feet from the source the intensity is 9 foot candles".
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9 = k/4^2
k = 9*16 = 144
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Equation:
I = 144/d^2
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What is the intensity 3 feet from the source.
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I = 144/3^2
I = 16 ft. candles
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Cheers,
Stan H.