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2023-02-18

The intensity of light produced by a light source varies inversely as the square of the distance from the source. If the intensity of light produced 3 feet from a light source is 750 foot-candles, find the intensity of light produced 5 feet from the same source. [4 MARKS]

Concept: 1 Mark
Application: 3 Marks
$\begin{array}{|cc|}\hline \text{Intensivity of light in foot candles}& \text{Distance from the source}\\ 750& 3\\ y& 5\\ \hline\end{array}$
$750\mathrm{\infty }\frac{1}{{3}^{2}}$
$750=\frac{K}{9}$
K=750×9
$y\mathrm{\infty }\frac{1}{{5}^{2}}$
$y=\frac{K}{25}$
$y=\frac{750×9}{25}$
y=270 foot candles

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