SOLUTION: im now sure i need HELP PLEASE If the illumination of a book 9m from a lamp is 150 lumens/m^2 find the illumination of the book 3m closer to the lamp... I got 225 lm/m^2?????????

Question 181362: im now sure i need HELP PLEASE
If the illumination of a book 9m from a lamp is 150 lumens/m^2 find the illumination of the book 3m closer to the lamp...
I got 225 lm/m^2?????????????????????
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
im now sure i need HELP PLEASE
If the illumination of a book 9m from a lamp is 150 lumens/m^2 find the illumination of the book 3m closer to the lamp...
I got 225 lm/m^2?????????????????????
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It's an inverse square relationship, common in nature.
i = k/d^2 (illumination = a constant/the distance squared)
150 = k/9^2
k = 150*81 = 12150
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@ 6 meters:
i = 12150/6^2 = 12150/36
i = 337.5 lm/m^2

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