The interaction between photons and electric and magnetic fields is fundamental to many physical processes, including the emission and absorption of light, the production of radio waves, and the behaviour of matter at the atomic and subatomic levels.
Photons & electric fields
Photons and electric fields are intimately connected in the framework of electromagnetic radiation.
When an electric field oscillates or changes, it generates electromagnetic waves.
This oscillation of the electric field gives rise to the emission of photons.
The energy of each photon is directly proportional to the frequency of the electric field oscillation.
Higher-frequency oscillations produce photons with higher energy, while lower-frequency oscillations produce photons with lower energy.
When photons interact with charged particles or materials with electric fields, they can be absorbed, transmitted, or scattered.
This interaction leads to phenomena such as the photoelectric effect, where photons can eject electrons from a material by transferring their energy to the electrons, and optical phenomena like reflection and refraction.
Photons & magnetic fields
When a photon interacts with a magnetic field, it can cause the magnetic field to oscillate, creating an electromagnetic wave.
This is because a magnetic field is one component of the electromagnetic field, which also includes an electric field.
When a photon interacts with the magnetic field, it transfers energy to it, causing the magnetic field to oscillate back and forth.
The oscillation of the magnetic field, in turn, creates an oscillating electric field, and the two fields together form an electromagnetic wave that propagates through space at the speed of light.
Fields
Fields refer to regions in space where a physical quantity is present that can exert a force or influence on other objects or particles.
Fields are used in physics to describe how certain properties or forces can vary with position and time.
In the case of electromagnetic fields, they represent the distribution of electric and magnetic properties in space.
An electric field is associated with electric charges and describes the force experienced by other charges (positive or negative) in its presence. Electric fields exist in the vicinity of charged objects and can exert forces on other charged particles.
A magnetic field is associated with moving electric charges, such as electric currents in wires, and it describes the force experienced by other moving charges (currents) in its vicinity. Magnetic fields exist around current-carrying conductors and can interact with moving charges, causing them to experience a magnetic force.
Electric, and magnetic forces, can be represented using vector fields.
In the case of an electric vector field, the vectors represent the electric force that a charged object would experience at different points in space due to the presence of other electric charges.
In the case of a magnetic vector field, the vectors represent the magnetic force that a moving charged object would experience at different points in space due to the presence of magnetic fields.
Fields are often represented in two dimensions using field lines.
The density of field lines indicates the strength of the field at a particular point – the more dense the lines, the stronger the field.
The conventions for how to show gravitational, electric, and magnetic field lines are all slightly different to model the unique aspects of each force. Some common models are shown below.