All About Photons

What is Time?

One second is 9.2 billion oscillations of a photon with 3.8×10⁻⁵ eVolts of energy.

Atomic Clocks: If one of these photons hits an electron sitting somewhere trapped in a Cesium atom at some energy level, it will be absorbed by that electron and cause that electron to "flip" its magnetic orientation. The Cesium atom is such that an upside down magnet is stable for a short time within the Cesium atom. Sometime later, that electron will "flip" back to it's normal magnetic orientation and will emit a photon with 3.8×10⁻⁵ eVolts of energy, allowing for continuous generation of photons with exactly 3.8×10⁻⁵ eVolts of energy.

Context: In our measurement of time, our clocks, depend on the gravity field that they are in. Specially, the photon oscillates slower in a high gravitational field (wavelength is longer). The photon still has the same energy, so it will still cause the electron to flip and your clock will run. This clock though, when compared to another clock in a lower gravitational field will have the number of oscillations per second different (less oscillations in the high gravity field), hence time runs slower in a high gravitational field.

Modelling Photons




The photon is a harmonic oscillator with a restoring potential known as the Planck constant (h). Planck’s constant, relates the amount of energy stored in a photon to its wavelength, E = h / λ. Put another way, Planck’s constant tells you the amount of time it takes the photon to undergo one cycle of whatever its doing given that the photon has a specific amount of energy.

Viewing the photon as a moving harmonic oscillator allows each oscillator to store a specific amount of energy. If you split the oscillator, you end up with two oscillators (photons), each of which has 1/2 the energy of the original oscillator (photon). The next step is to put these photons in motion and watch them interact with each other in a small cavity over a period of time.

Oscillating photons of one energy level are generated at random locations throughout a resonating cavity. A partially reflective mirror lets some photons 'leak' out one side. Photons only 'leak' past the mirror if their electrical phase is at a minimum and is growing. All photons emitted from the laser have a common starting point and phase, producing a cohearent laser beam.

The Michelson interferometer is used to measure tiny differences in length along two different light paths. A laser light source is split into two arms with a beamsplitter. Each arm is reflected back toward the beamsplitter which then combines their amplitudes. The resulting interference pattern will record a fringe pattern.

 
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