Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 2 - Test - Page 434: 29


45 foot-candles

Work Step by Step

Consider $ I $ to be the intensity and $ d $ to be the distance of the source. We have $ I=\dfrac{k}{d^2}$ ....(1) so, $20=\dfrac{k}{225}$ This implies that $ k=4500$ Equation (1) becomes: $ I=\dfrac{4500}{(10)^2}=45$ Therefore, the intensity of a light at a distance 10 feet from the source is 45 foot-candles.
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