Question 461960
Astronomers can use the brihtness of two light sources,such as stars, to compare the distances from the light sources.The intensity , or brightness, of light I is inversely proportionnal to the square of the distance from the light source d.
a) write an equation that represents this situation.
Ans: I = k/d^2
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b) if d is the independent variable and I is the dependent variable,graph the equation from exercise a when k=16
I = 16/d^2
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{{{graph(400,300,-10,10,-10,10,16/x^2)}}}
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c) if two people are viewing the same light source,and one person is three times the distance from the light source as the other person,compare the light intensities t
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intensity for person closer to sight source = k/d^2
intesity for person further away = k/(3d)^2
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Compare the two by dividing: [k/d^2]/[k/(3d)^2] = (k/d^2)*[(3d)^2/k] = 9

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The intesity for the person closer to the light source 
is 9 times as great as for the person further away from 
the light source.
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Cheers.