Author: John Mulindi
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Limitations of Bohr’s Quantum Theory of Spectra
Even though Niels Bohr’s quantum theory of spectra was regarded as one of the most revolutionary and successful theory of atomic dynamics, it was limited in the following ways: To overcome some of these limitations, Louis Victor de Broglie hypothesized that because photons have wave and particle characteristics, perhaps all forms of matter have wave…
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Black Hole Evaporation Phenomenon
The discovery of a temperature seen by an accelerated fiducial observer adds a new dimension to the equivalence principle. Identical thermal effects can be expected to happen near the horizon of a very massive black hole. Nonetheless, in the case of a black hole a new phenomenon can take place, that is, evaporation. In contrast…
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Demystifying Compton Scattering
As the incident photon energy increases, the likelihood that it will undergo Photoelectric Effect decreases and the Compton Effect also referred to as Compton scattering becomes the dominant mode of interaction. In Compton scattering, the incident photon with energy hv0 interacts with a loosely bound (or free) electron from an outer shell and transfers some…
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The Decay of Black Holes
Black holes are areas of space where the gravity is so strong that nothing, not even light can escape. However, that was the understanding held until 1974, when the astrophysicist Stephen Hawking proposed that black holes are indeed radiant objects, emitting a variety of particles by a mechanism involving tunnelling through the (gravitational) potential barrier…
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The Fundamentals of Electromagnetic Waves
Electromagnetic waves are electric and magnetic fields traveling through free space at the speed of light; in other words, an electromagnetic wave is a propagating electromagnetic field that travels with finite velocity as a disturbance through a medium. The field itself is the disturbance, rather than simply representing a physical displacement or other effect on…
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What is Dark Matter?
The largest contribution to the mass of the universe is believed to come from dark matter (i.e. matter that we can’t see). This dark matter is inferred to exist from studies of the motion of outlying stars, orbiting galaxies, the motion of galaxy clusters and from images formed by gravitational lenses (composed of clusters of…
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What are Atom Traps?
Atoms that are cooled below a millikelvin can also be held in space with either static magnetic fields, laser fields, or a combination of a weak magnetic field and circularly polarized light. Atoms traps can be used to accumulate a large number of laser-cooled atoms; confine them for further cooling and use them for studies…
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Lightning as an Electrical Phenomenon
Friction produces electric charges high in the atmosphere. This occurs when small particles such as water droplets and ice collide or rub against one another. Wind, among other factors, separates these charges and large electric forces develop between the ground and the air above. The atmospheric charges and fields have strong effects. Opposite charges attract…
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The Principle & Application of Nuclear Magnetic Resonance (NMR)
Nuclear magnetic moments (along with electronic magnetic moments) precess (spin) when placed in an external magnetic field, B. The frequency at which they precess, called the Lamor precessional frequency, wL, is directly proportional to the magnetic field. When the magnetic moment μ is lined up with the field as closely as quantum physics permits, the…
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The Physics Behind Magnetic Resonance Imaging (MRI)
MRI provides physicians with a tool to assess a patient’s health. To have an MRI exam, the patient lies in a very strong magnetic field that is generated by powerful magnets. The MRI machine then applies radio waves to the patient’s body; radio waves are electromagnetic waves. MRI uses radio waves as this kind of…