Category: Wave Particle Duality

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,… Continue reading 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,… Continue reading PARTICLE-WAVE DUALITY IN THE MACROSCOPIC WORLD

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,… Continue reading A SIMPLE TEM

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… Continue reading TWO-SLIT INTERFERENCE WITH SINGLE ELECTRONS

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… Continue reading EXPERIMENTAL CONFIRMATION OF DE BROGILE’S MATTER WAVES

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… Continue reading MATTER WAVES AND THE BOHR ATOM

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… Continue reading MATTER WAVES

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… Continue reading THE ANSWER: COMPLEMENTARITY

A regular TV camera wouldn’t be able to detect anything at the low-photon flux we need to ensure only one photon passes the slits at a time. An “image-intensifier tube”—like those used by soldiers to see at night—is needed to make the image visible to a conventional camera element (e.g., a CCD camera). In our… Continue reading IMAGING SINGLE PHOTONS

Taylor exposed photographic plates for up to 3 months to obtain interference patterns using his very weak light source. Today, we can conduct the same experiment within a few minutes, using the setup shown in the block diagram of Figure 90. The basic idea remains the same—to illuminate the double slit with a very weak beam.… Continue reading TWO-SLIT INTERFERENCE WITH SINGLE PHOTONS