Conceptual Physics (12th Edition)

Published by Addison-Wesley
ISBN 10: 0321909100
ISBN 13: 978-0-32190-910-7

Chapter 26 - Think and Discuss - Page 502-503: 92


Energy is spread out over a larger area, so the light is less intense, but not lost.

Work Step by Step

For example, when we are three times as far away, the light is one-ninth as bright, but there is 9 times the surface area that the light is illuminating. The total amount of light (i.e., the light energy) falling on a spherical surface is the same, at any distance from the light source.
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