SOLUTION: The intensity of light​ (in foot-candles) varies inversely as the square of​ x, the distance in feet from the light source. The intensity of light 2 feet from the sourc
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Question 1072077: The intensity of light (in foot-candles) varies inversely as the square of x, the distance in feet from the light source. The intensity of light 2 feet from the source is 20 foot-candles. How far away is the source if the intensity of light is 5 foot-candles?
Answer by rothauserc(4718) (Show Source): You can put this solution on YOUR website!
let k be the constant of proportionality, then
:
I = k / x^2
:
we are given I = 20 and x = 2, then
:
20 = k / 2^2
:
k = 80
:
for I = 5, we have
:
5 = 80 / x^2
:
x^2 = 80 / 5 = 16
:
x = square root(16) = 4
:
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The source is 4 feet away
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