- 3646 - PHOTONS - are particles of light energy? A photon is the smallest discrete amount or quantum of electromagnetic radiation. It is the basic unit of all light. Photons are always in motion and, in a vacuum, travel at a constant speed to all observers of 2.998 x 108 meter / second, or 186,000 miles per second.
--------------------- 3646 - PHOTONS - are particles of light energy?
- The speed of light is denoted by the letter “c“. Einstein’s light quantum theory states photons have energy equal to their oscillation frequency times Planck’s constant,
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---------------------------------- “c = h * f “
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- Einstein proved that light is a flow of photons, the energy of these photons is the height of their oscillation frequency, and the intensity of the light corresponds to the number of photons. A stream of photons can act both as a wave and particle.
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---------------------------------- The basic properties of photons are:
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---------------- They have zero mass and rest energy. They only exist as moving particles.
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---------------- They are elementary particles despite lacking rest mass.
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---------------- They have no electric charge.
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---------------- They are stable.
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---------------- They are spin-1 particles which makes them bosons.
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---------------- They carry energy and momentum which are dependent on the frequency.
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---------------- They can have interactions with other particles such as electrons, such as the Compton effect.
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---------------- They can be destroyed or created by many natural processes, for instance when radiation is absorbed or emitted.
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---------------- When in empty space, they travel at the speed of light.
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- Light and magnetism are affections of the same substance, and light is an electromagnetic disturbance propagated through the field according to electromagnetic laws, wrote Maxwell in 1865.
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- On 14 December 1900, Max Planck demonstrated that heat radiation was emitted and absorbed in discrete packets of energy. He called “quanta“. Later, Albert Einstein showed in 1905 that this also applied to light. Einstein called a quantum of light.
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- Einstein believed light is a particle (photon) and the flow of photons is a wave. The German physicist was convinced light had a particle nature following his discovery of the photoelectric effect, in which electrons fly out of a metal surface exposed to light. If light was a wave, that couldn’t have happened.
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- Another puzzling matter is how photoelectrons multiply when strong light is applied. Einstein explained the photoelectric effect by saying that “light itself is a particle”. Einstein’s light quantum theory is that light’s energy is related to its oscillation frequency.
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- Einstein maintained that photons have energy equal to “Planck’s constant times oscillation frequency,” and this photon energy is the height of the oscillation frequency while the intensity of light corresponds to the number of photons.
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- Light is a flow of photons, the energy of these photons is the height of their oscillation frequency, and the intensity of the light is related to the number of photons.
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- Einstein was able to prove his theory by deriving Planck’s constant from his experiments on the photoelectric effect. His calculations rendered a Planck’s constant value of 6.6260755 * 10^-34 which is exactly what Max Planck obtained in 1900 through his research on electromagnetic waves.
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- A clever experiment in 2015 had a laser used to fire onto a nanowire, causing electrons to vibrate. Light travels along this tiny wire in two possible directions. When waves traveling in opposite directions meet each other they form a new wave that looks like it is standing in place.
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- This standing wave becomes the source of light for the experiment, radiating around the nanowire. They fired a new beam of electrons to image the standing wave of light, which acts as a fingerprint of the wave-nature of light.
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- In 2016, Polish physicists created the first ever hologram of a single light particle. The team at the University of Warsaw made the hologram by firing two light beams at a beam splitter, made of calcite crystal, at the same time.
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- The beam splitter is akin to a traffic light intersection so each photon can either pass straight through or make a turn. When a photon is on its own, each path is equally probable but when more photons are involved they interact and the odds change.
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- If you know the wave function of one of the photons, it’s possible to figure out the shape of the second from the positions of flashes appearing on a detector. The resulting image looks a bit like a Maltese cross, just like the wave function predicted from Schrödinger’s equation.
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- Not only is light made up of photons, but all electromagnetic energy : microwaves, radio waves, X-rays is made up of photons. Light behaves both like a wave and a particle is called the wave-particle duality theory.
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- Photons are always electrically neutral. They have no electrical charge.
Photons do not decay on their own.
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- The electromagnetic force effects of this force are easily observable at both the microscopic and macroscopic level, because the photon has no rest mass; this allows for interactions at long distances.
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- Like all elementary particles, photons are governed by “quantum mechanics” and exhibit “wave-particle duality“, properties of both waves and particles. A single photon may be refracted by a lens or exhibit wave interference, but also act as a particle giving a definite result when its location is measured.
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- The photon model accounted for the frequency dependence of light's energy, and explained the ability of matter and radiation to be in thermal equilibrium. It also accounted the properties of black body radiation.
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- Photons are described as a necessary consequence of physical laws having a certain symmetry at every point in spacetime. The intrinsic properties of photons, such as charge, mass and spin, are determined by the properties of this “gauge symmetry“.
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- The photon concept has led to momentous advances in experimental and theoretical physics, such as lasers, Bose–Einstein condensation, quantum field theory, and the probabilistic interpretation of quantum mechanics.
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- It has been applied to photochemistry, high-resolution microscopy, and measurements of molecular distances. Photons have been studied as elements of quantum computers and for sophisticated applications in optical communication such as quantum cryptography.
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- Physicists have used lasers to deep-freeze antimatter. An ultraviolet laser quelled the thermal jitters of anti-hydrogen atoms, chilling the anti-atoms to just above absolute zero.
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- This technique for slowing down antimatter, the oppositely charged counterpart to normal matter, could help scientists build the first antimatter molecules. Taming unruly antimatter with laser light may also allow physicists to measure the properties of anti-atoms much more precisely. Comparing anti-atoms with normal atoms could test some fundamental symmetries of the universe.
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- To craft anti-hydrogen atoms scientists mixed antiprotons with positrons, the antiparticles of electrons, at the CERN particle physics lab near Geneva. Over several hours, a laser beam tuned to a specific frequency of UV light slowed the anti-hydrogen atoms from whizzing around at up to 90 meters per second to about 10 meters per second.
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- Supercooled anti-hydrogen could test an idea called “charge-parity-time“, or CPT, symmetry. This physics principle says that normal atoms should absorb and emit photons with the exact same energies as their antimatter look-alikes. Even the tiniest differences between hydrogen and anti-hydrogen could undermine modern theories of physics.
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- Einstein’s theory of gravity predicts that matter and antimatter should fall to Earth at the same rate. Lab experiments dropping laser-cooled anti-atoms, instead of warm, jittery ones, into free fall could provide a clearer view of gravity’s effects.
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August 9, 2022 PHOTONS - are particles of light energy? 3646
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