I will read it Dave bit busy atm as a pool cleaner, barman, head cook, and bottle washer
All electromagnetic waves, from radio waves with wavelengths L~km to gamma-rays with L~10e-12 m (i.e. 1 picometre, or 1 pm), are made up of bundles of energy called `photons'. This is a consequence of the `uncertain' quantum nature of EM radiation, where each energy bundle has E = hf (J = Joules), where h = Planck's constant (very small: 6.626e-34 J.s), and f = c/L is the EM radiation frequency in Hertz (Hz), and c = speed of light in the medium (c = 2.998e8 m/s in vacuum). So EM radiation can show `classical' wave-like properties in some situations, and `classical' particle-like properties in others. `Classical' here refers to the physicists' worldview pre-Quantum Revolution of the 1900s-1920s. Wave-like behavior is experimentally seen in interference and diffraction phenomena, when there is a relatively large number of photons, each of small energy (this happens when the wavelength L is larger than the size of the interaction region, e.g. a barrier's slit width). Particle-like `photon' behavior is experimentally seen when the wavelength L is smaller than the interaction region, i.e. when there are relatively fewer photons, each of high energy. Waves (consisting of many `photons', which are not directly seen themselves) will interfere with each other, diffract around corners, and spread out isotropically in all directions if emitted unobstructed by point-like oscillators. Particles or `photons' can be detected by being captured in `pixel' detectors in a CCD camera array, which is designed to absorb the small amounts of photon energy E = hf for the wavelength L of interest. According to a well-known interpretation of quantum physics, first proposed by Danish Prof. Niels Bohr in the 1920s, this quality of wave-particle duality is an unavoidable consequence of the quantum mechanical uncertainty principle - he called this an example of `complementarity' (this now being a philosophical claim about physical reality). The basic conclusion is that the quantum nature of EM radiation is a physical reality confirmed to excellent precision by experiment, and which is very different (and sometimes difficult to appreciate and understand) from the textbook `classical physics' worldview held by such pre-20th century visionary physicists such as Isaac Newton (gravitation theory) or James Clerk Maxwell (electromagnetic theory). It turns out that a 20th-century physicist, Albert Einstein, who overthrew and replaced Newton's gravitation theory with his own more encompassing General Theory of Relativity, was one of the key founders of the new
Quantum Physics - but even Einstein had heated debates with
Niels Bohr about the nature of physical reality, and over how exactly to interpret how the new quantum physics experimental results (e.g. spectral line wavelength shifts and splittings) could be explained by a more detailed underlying physical picture and model. The main problem here is to come to grips with how a measurement of fundamental particles is made, and how it might be mathematically modeled. This `measurement problem' is apparently necessarily at the mercy of the
quantum uncertainty principle, and this is viewed with dislike by those who believe that the underlying mathematical physical model should be deterministic, i.e. ultimately *not* left to irreducible randomness. This was a key point of contention between Einstein and Bohr in the 1930s, which was actually brought face-to-face with actual physical reality in the well-known Einstein-Podolsky-Rosen (EPR) experiment, initially only a `thought experiment' in the 1903s EPR journal paper, but then carried out by Alain Aspect et al. in the late 1970s with a physical apparatus, configured to test for the so-called Bell inequalities. The result from these EPR experiments seems to be that Bohr's uncertainty and randomness are shown to be present as always and that the quantum physics equations work perfectly well. If there is an underlying physical theory that can predict the results of these EPR experiments, then they seem to have spooky `non-local' effects, which are nowadays taken as evidence for a purely
quantum phenomenon called `entanglement'. This new insight is likely to be a key point in the realisation of new physical theories and devices, such as in a quantum gravity theory for black holes and our universe (or multiverse), and in the hoped-for quantum computers which should be able to crack any of the current-day encryption codes.
So, the humble `photon' concept has taken us a long way in physics, as well as in our understanding and perhaps future mastery of the physical universe in which we find ourselves!Verpies I still not have watched all 3.5hrs of that stream
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If it was so then a path of a laser beam passing through the solenoid would be affected, but it is not.
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It seems that the wavelength and proximity of the solenoid (diameter) makes a difference to interference.
Regards
Mike
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860
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Topic: PHOTONS AND PHONONS OPEN DISCUSSION (Read 4307 times)
