Conceptual Physics (12th Edition)

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

Chapter 27 - Think and Explain: 51

Answer

Water absorbs red light. Deep underwater, any sunlight that has made it all the way there is cyan (red's complementary color), because the red has been absorbed on the way. Red blood absorbs cyan and reflects red, so deep underwater, photos taken with natural light make blood appear to be black. If a camera flash is used, there is plenty of red light available to reflect, so the blood looks red again.

Work Step by Step

This is discussed on pages 514-515.
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.