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# Power Functions

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Write a power function for the following situation, and then use the equation to solve for the missing information. The intensity I of light varies inversely as the square of the distance D from the source. If the intensity of illumination on a screen 5 feet from a light is 2 foot-candles, find the intensity of illumination on a screen 5 feet from the light.

Oct 18, 2017

#1
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Did you ask the correct queston???...we aleady know the intensity 5 feet from the light....   Oct 18, 2017
#2
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Oh! The second 5 feet is supposed to be 15 feet.

Oct 18, 2017
#3
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OK.....!!!

Here's the equation we need

I  =  k / D^2   .....  and we need to find the proportionality constant, "k"....

So we have....

2  = k / 5^2

2 = k / 25       multiply both sides by 25

50  = k

And we need to solve this

I  =  50 / 15^2

I  = 50 / 225

I = 10 / 45   =   2 / 9  foot-candles   Oct 18, 2017
edited by CPhill  Oct 18, 2017
edited by CPhill  Oct 18, 2017
#4
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Thanks!

AdamTaurus  Oct 18, 2017