How de Broglie Showed that All Particles Display Wave-Like Properties

In 1923, the physicist Louis de Broglie suggested that not only did waves exhibit particle-like aspects, but that the reverse was also true — all material particles should display wave-like properties.

How does this work? For a photon, momentum

image0.png

And the wave vector, k, is equal to

image1.png image2.png

De Broglie presented these apparently surprising suggestions in his Ph.D. thesis. Researchers put these suggestions to the test by sending a beam through a dual-slit apparatus to see whether the electron beam would act like it was made up of particles or waves. In the figure, you can see the setup and the results.

An electron beam going through two slits.
An electron beam going through two slits.

In Figure a, you can see a beam of electrons passing through a single slit and the resulting pattern on a screen. In Figure b, the electrons are passing through a second slit. Classically, you’d expect the intensities of Figures a and b simply to add when both slits are open:

I = I1 + I2

But that’s not what happened. What actually appeared was an interference pattern when both slits were open (Figure c), not just a sum of the two slits’ electron intensities.

The result was a validation of de Broglie’s invention of matter waves. Experiment bore out the relation that

image4.png

and de Broglie was a success.

The existence of matter waves says that you add the waves’ amplitude,

image5.png

not their intensities, to sum them:

image6.png

You square the amplitude to get the intensity, and the phase difference between

image7.png

is what actually creates the interference pattern that’s observed.

  • Add a Comment
  • Print
  • Share
blog comments powered by Disqus
Advertisement

Inside Dummies.com

Dummies.com Sweepstakes

Win $500. Easy.