Einstein called these energy packets photons, and these are now recognised as a fundamental particle. Visible light is carried by photons, and so are all the other kinds of electromagnetic radiation like X-rays, microwaves and radio waves. In other words, light is a particle.

Single-photon isolation using chiral light-matter interaction. A single-photon isolator and circulator can be achieved by chirally coupling a quantum emitter to a passive, linear nanophotonic waveguide or a WGM microresonator which possesses optical chirality.

Each photon has a wavelength and a frequency. The wavelength is defined as the distance between two peaks of the electric field with the same vector. The frequency of a photon is defined as how many wavelengths a photon propagates each second. Unlike an electromagnetic wave, a photon cannot actually be of a color.

The energy for one photon is usually calculated by E = hf where f is the light frequency. Since for a light wave, f = c / λ, we can combine the two equations and use E = hc/λ. This eliminates having to find the frequency and just saves a little time. The wavelength should be converted from 679 nm to 6.79 x 10-7 m.

An unaccelerated, free electron can only emit 1 photon, when being annihilated by colliding with a positron. Both particles will be converted into one photon each, each having an energy of 0.511 MeV. There is also synchrotron/cyclotron radiation, which can produce any number of photons.

The photon has only energy and no mass. When the photon gives up all its energy to an electron the photon disappears. The electron on the other hand, has mass and charge – electrons carry the electrical current in wires. Photons at extreme energies (millions of electron Volts of energy) can create electrons.

“The electrons could not absorb more than one photon to escape from the surface, they could not therefore absorb one quanta and then another to make up the required amount – it was as if they could only embrace one quantum at a time. Each photon of blue light released an electron.

When the electron changes levels, it decreases energy and the atom emits photons. The photon is emitted with the electron moving from a higher energy level to a lower energy level. The energy of the photon is the exact energy that is lost by the electron moving to its lower energy level.

When an electron is hit by a photon of light, it absorbs the quanta of energy the photon was carrying and moves to a higher energy state. Electrons therefore have to jump around within the atom as they either gain or lose energy.

in a vacuum, photons are always faster than electrons. the speed of light in glass, air, water, etc. is actually slower than the speed of light in a vacuum.

From the perspective of a photon, there is no such thing as time. It’s emitted, and might exist for hundreds of trillions of years, but for the photon, there’s zero time elapsed between when it’s emitted and when it’s absorbed again. It doesn’t experience distance either.

approximately 500 km