Conceptual Physics (12th Edition)

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

Chapter 28 - Think and Explain - Page 540-542: 70


During a lunar eclipse the moon is not totally dark, but appears reddish, though it is in Earth’s shadow.

Work Step by Step

Figure 28.19 shows how the Earth's atmosphere acts as a converging lens that refracts light into the shadow region. (Figure 28.18 may also be helpful.) Blue light is scattered more strongly in the atmosphere, so it is mostly reddish light that makes it through the tortuous path, to finally fall upon the moon. In other words, the moon appears red during a lunar eclipse because of the refraction of Earth’s sunrises and sunsets.
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