Author: Haroon Khalil
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WAVEFUNCTIONS
Now, this brings up an interesting question: if a sound wave is a vibration of matter, and a photon is a vibration of electric and magnetic fields, what exactly vibrates when matter acts as a wave? The upsetting answer is that there is no directly measurable quantity to correspond to the matter wave itself. This…
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Introduction
We presented de Broglie’s proposal that wave–particle duality works for matter in the same way it does for light. That is, although light usually behaves as an electromagnetic wave, it sometimes acts as a particle (photon). At the same time, while electrons mostly behave as particles in CRTs, they sometimes exhibit wave-like behavior. We also…
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PARTICLE-WAVE DUALITY IN THE MACROSCOPIC WORLD
If all matter has wave-like properties, why is it that we don’t observe quantum effects in our daily lives? Consider, for example, the de Broglie wavelength of a 0.15-kg baseball batted at 30 m/s: At that wavelength, a baseball would need to interact with objects smaller than subatomic particles to show quantum effects. In summary,…
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PARTICLE-WAVE DUALITY IN THE MACROSCOPIC WORLD
If all matter has wave-like properties, why is it that we don’t observe quantum effects in our daily lives? Consider, for example, the de Broglie wavelength of a 0.15-kg baseball batted at 30 m/s: At that wavelength, a baseball would need to interact with objects smaller than subatomic particles to show quantum effects. In summary,…
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A SIMPLE TEM
Systems to observe single-electron interference have been built by other groups, and a committed experimenter‡ who would like to build such a device should study the excellent papers written by these research groups. This will help you to gain an understanding of how they overcame some of the difficult technical challenges involved. Even with today’s technology,…
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TWO-SLIT INTERFERENCE WITH SINGLE ELECTRONS
De Broglie’s critics argued that the results from electron-diffraction experiments may indicate an undulating interaction between electrons, so these experiments didn’t decisively prove that electrons are waves when studied by diffraction. Definitive proof would still have to wait until technology advanced to make it possible to conduct the double-slit experiment with individual electrons. In one of his…
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EXPERIMENTAL CONFIRMATION OF DE BROGILE’S MATTER WAVES
Experimental confirmation of de Broglie’s formula came in 1927, when G. P. Thomson at the University of Aberdeen and C. J. Davisson with L. H. Germer at Bell Labs observed diffraction—a typical wave-like behavior—from an electron beam. Unlike photons, electrons have a rest mass, and are thus perceived as “solid” particles. Electrons are negatively charged…
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MATTER WAVES AND THE BOHR ATOM
Bohr was able to explain the discrete spectral lines emitted by the hydrogen atom by forcing the electrons into a limited number of permitted orbits (Figure 94a). However, like Planck before him, he did this without having a physical justification. Figure 94 De Broglie used his proposed matter waves to explain why Bohr’s atomic orbits would…
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MATTER WAVES
Even in the light of the Compton Effect, critics of the early single-photon interference experiments dismissed the importance of the observation by noting that a photon doesn’t have mass. Through some fancy hand-waving, they argued that the low-light interference could be caused through splitting and recombining the light quanta’s wavefront. Decisive proof would come when…
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THE ANSWER: COMPLEMENTARITY
So, yet again, what is the answer? Is light a wave, or is light a stream of particles? Well, actually it’s neither (or both). Light apparently is something different altogether, but it behaves as a wave when the experiment is designed to reveal its wave-like properties, while it behaves as a particle when the experiment is designed to show…