Conceptual Physics (12th Edition)

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

Chapter 31 - Think and Discuss: 65


Red photons have less energy than blue photons. Blue light can expose the film. It would be safer to have bright red light than very dim blue light.

Work Step by Step

Red light has insufficient energy per photon to trigger the chemical reaction in the film. Bright red light just means more photons, each of which can't cause a reaction, so it is still safe. Blue light has enough energy per photon to expose the film, so the less blue light, the better.
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