Question 1173968
the intensity I of illumination from a light source is inversely proportional to the square of the distance d from the source.
make an equation from this information given
I = {{{k/d^2}}} where 
 I=illumination in candelas;
 d=distance from light source, 
 k=constant
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Suppose the intensity is 320 candela at a distance of 10 feet from a light source.
Find k with these values
{{{k/10^2}}} = 320
k = 320 * 100
k = 32000
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a. What is the intensity at 2 feet from the​ source?
I = {{{32000/2^2}}}
I = 8000 candelas
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b. How far away from the source will the intensity be 400 ​candela?
400 = {{{32000/d^2}}} 
400d^2 = 32000
d^2 = {{{32000/400}}}
d^2 = 80
d = {{{sqrt(80)}}}
d = 8.9 ft
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