Author: workhouse123
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BYE, BYE CLOCKWORK UNIVERSE
Isaac Newton realized that the laws of motion he had discovered, including the Law of Universal Gravitation, could explain, at least in principle, the behavior of all physical objects in the universe known at the time. These physical laws were so powerful they allowed scientists of the time to calculate with accuracy the movements of…
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FOURIER ANALYSIS
When we separated light into its constituent lines, or binned scintillation photons according to their energy, we were performing spectral analysis. Since light and gamma rays most commonly act as waves, what we have been doing is deconstructing a complex electromagnetic wave into many simple sine waves. The same method can be applied to the…
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TIME–ENERGY UNCERTAINTY
Bohr realized that if there is an uncertainty relationship between momentum p and position x: which comes from quantizing momentum as a function of wavelength: A similar uncertainty principle must then exist between energy E and time t. This is because: where frequency is the inverse of a time interval f = 1/t, so: Indeed, an identical relationship exists for the product of…
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EXPERIMENTAL DEMONSTRATION OF THE UNCERTAINTY PRINCIPLE
A demonstration of the Uncertainty Principle is simple to conduct using a laser pointer and an adjustable slit consisting of two razor blades. The idea is that the photons emitted by the laser travel without diverging. As shown in Figure 104, the photons exiting the laser can be assumed to have momentum only along the x axis (so py =…
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THE UNCERTAINTY PRINCIPLE
In 1925, German physicist Werner Heisenberg was an assistant to Niels Bohr at the Institute of Theoretical Physics at the University of Copenhagen. Heisenberg’s research related to the development of mathematical operations to calculate the expected results of experiments on hydrogen atoms based only on observables—that is, using only quantities that could be experimentally measured,…
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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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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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BLURRING THE LINE BETWEEN QUANTUM AND CLASSICAL
Electrons are still very small particles, so the question arises as to whether quantum weirdness extends to larger objects. The experimental answer is yes! In 1988, Austrian physicist Anton Zeilinger performed the basic interference experiment with neutrons.29 In 1991, Carnal and Mlynek did the same with helium atoms.30 In 1999, Markus Arndt, Anton Zeilinger, and co-workers31 at the…
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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…