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Wave-Particle Theory

Electromagnetic radiation behaves as both a wave and a particle depending on how it is observed.

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Laser Love

Laser Love

Credit: Brian Chow
Source: http://www.flickr.com/photos/free-stuff/188871687
License: CC BY-NC 3.0

Lasers like the one in this bar code scanner are a staple of modern life. Lasers are used in many different devices, from CD and DVD players to the instruments doctors use to perform laser eye surgery. You would probably find it difficult to go through your day without interacting with lasers in some way.

Amazing But True!

  • It’s hard to believe that just a few decades ago, when lasers were invented, they were thought to have no practical value.
  • Even more amazing, the scientific theory that led to the invention of the laser is one of the strangest theories in science. This is Einstein’s wave-particle theory. According to the theory, electrons can be stimulated to give off light energy that behaves like both a particle and a wave. We now call these particles of light energy photons.
  • Credit: Kara Murphy
    Source: https://www.flickr.com/photos/karaem23/4485432507
    License: CC BY-NC 3.0

    Music concerts utilize lasers to enhance the viewers experience [Figure2]

  • The theory is strange not only because it’s impossible to envision something that both is and isn’t a particle.
  • The theory has also lead to some odd revelations. For example, the mere act of observing photons changes them, and photons seem to “love” to be with other photons.
  • Einstein himself even said that the more we know about the theory, “the sillier it looks.” Yet this theory has revolutionized our understanding of nature.
  • So how do lasers work and what do they have to do with Einstein’s “silly” theory? Watch this very short video to find out:


Show What You Know

With the links below, learn more about wave-particle theory and lasers. Then answer the following questions.

  1. How is laser light different from the light produced by a flashlight?
  2. How is laser light produced?
  3. What is the function of the mirrors in a laser device?
  4. How is laser light able to cut materials such as fabric? 
  5. How is the laser related to wave-particle theory?
  6. What are some other inventions that are real-world applications of the theory? These could be inventions already in use or those that may be possible in the future.

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Image Attributions

  1. [1]^ Credit: Brian Chow; Source: http://www.flickr.com/photos/free-stuff/188871687; License: CC BY-NC 3.0
  2. [2]^ Credit: Kara Murphy; Source: https://www.flickr.com/photos/karaem23/4485432507; License: CC BY-NC 3.0

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