Electromagnetic force

• The electromagnetic force is a fundamental force, its effects manifest as the push and pull interactions between charged particles.
• This means this force is not derived from anything else. It cannot be further broken down or explained by simpler forces.
• Even though the nature of the electromagnetic force is not fully understood, classical physics and quantum mechanics can provide a precise understanding of its emergence from charged particles, its behaviour, and the interactions it governs.
• It is one of the four most basic and essential forces in the universe. These four forces exist independently of each other, although they can interact and influence each other in certain situations.

Protons, electrons & photons

• The electromagnetic force, mediated by the exchange of photons, arises in the presence of and from the movement of electrically charged particles such as protons and electrons within atoms.
• Protons are positively charged and electrons are negatively charged. Due to the electromagnetic force like charges attract one another whilst opposite charges repel.
• This push and pull process is likely to take one of three forms:
  • 1. The push and pull that holds an atom together
    • The force holding an atom together is primarily the electrostatic force which is a specific aspect of the electromagnetic force.
    • This force arises from the attraction between oppositely charged particles within an atom. Protons (positively charged) in the nucleus attract electrons (negatively charged) surrounding the nucleus.
    • This attraction is mediated by the exchange of virtual photons. These virtual photons constantly fluctuate in the electromagnetic field and carry the influence of the force between the charged particles.
    • A virtual photon is a temporary fluctuation in the electromagnetic field and cannot be directly observed.
  • 2. Push and pull below the threshold of an electron transition
    • This refers to the continuous, underlying force between charged particles in an atom, even when it does not produce an electron transition.
    • This doesn’t involve emitting or absorbing a real photon but rather the ongoing exchange of virtual photons mediating the attraction or repulsion.
    • Even when an atom is in its ground state, the electromagnetic force keeps electrons in their specific orbitals due to this continuous exchange. The force’s strength might vary depending on the distance and arrangement of charges within the atom, but real photons aren’t emitted or absorbed as long as the electrons remain in the same energy level.
  • 3. Force that causes an electron transition
    • This case represents a change in the existing electromagnetic force rather than a separate force.
    • When an atom absorbs energy (e.g., from light), an electron can be excited to a higher energy level.
    • The absorbed energy (which could be in the form of a real photon) provides the impetus for the electron to overcome the attraction from the nucleus and move to a higher energy orbital.
    • No real photon is emitted during the absorption process itself.
    • The emission of real photons only occurs when an electron transitions from a higher energy level to a lower one.
    • In this case, the transition involves the emission of a real photon with an energy equal to the difference in energy levels between the initial and final states.
    • This emission signifies the release of energy by the electron and is a consequence of the existing electromagnetic force, not a separate force itself.

Real photons

• Real photons are fundamental particles that carry electromagnetic force over long distances. They are massless and travel at the speed of light in a vacuum.
• Unlike virtual photons, which are temporary fluctuations in the electromagnetic field, real photons exist independently and can be detected or measured.
• The visible light we see originates from real photons emitted by various sources, such as stars, light bulbs, and even fireflies.
• The different colours of light correspond to different frequencies of these photons.
• Radio waves, microwaves, and X-rays are also examples of electromagnetic radiation consisting of real photons with different frequencies and energies.

Characteristics of real photons

• Quantized energy: They come in discrete packets of energy, with the energy of each photon directly proportional to its frequency.
• Electromagnetic spectrum: Different frequencies of real photons correspond to different parts of the electromagnetic spectrum, encompassing visible light, radio waves, X-rays, and more.
• Light source: Real photons are emitted by various light sources when electrons in atoms or molecules undergo transitions between energy levels. The specific energy of the emitted photon corresponds to the difference in energy levels between the initial and final states of the electron.