Conceptual Physics (12th Edition)

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

Chapter 21 - Think and Explain: 70

Answer

Blue laser light spreads out less than red laser light does when you are trying to create a thin beam.

Work Step by Step

As you know when you have tried to shine a flashlight across a room, a beam of light tends to spread out with distance, i.e., the spot size of the beam gets wider and wider. Blue light has a shorter wavelength than other wavelengths of visible light (especially the ubiquitous red HeNe laser) and stays better collimated. The key term is "diffraction", the tendency of a wave to bend around the corners of a barrier (or a hole) into the region that you'd expect to be in shadow. Blue laser light diffracts less than red laser light does and can form a tighter beam.
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