When an element or compound is heated, it undergoes a process called emission, where it releases (emits) particles or electromagnetic radiation across a range of wavelengths, including visible light, as a result of electron transitions or atomic/molecular vibrations.

Types of Emission
  • Electromagnetic radiation: The emission of photons, which are the energy packets of light and include electromagnetic waves like X-rays, gamma rays, radio waves, etc.
    • Electrons transition from higher to lower energy levels in atoms, emitting a photon with specific energy.
    • Radioactive nuclei decay, emitting high-energy photons like gamma rays.
  • Particle emission: This involves the emission of subatomic particles themselves, such as electrons, neutrons, protons, or alpha particles.
    • Radioactive nuclei decay emits alpha particles or beta particles (electrons or positrons).
    • Neutron stars can emit streams of charged particles in a phenomenon called “pulsar wind.”
Causes of Emission
  • Energy transitions: When a subatomic particle transitions from a higher energy state to a lower one, it emits the excess energy as radiation or particles.
  • Instability: Radioactive nuclei are unstable and undergo decay to reach a more stable configuration, emitting energy and particles in the process.
  • External interactions: Subatomic particles can be struck by other particles or radiation, leading them to emit energy or new particles.
Consequences of Emission
  • Most of the light and energy we perceive around us arises from subatomic emission processes in stars, atoms, and molecules.
  • Understanding subatomic emission is crucial for studying radioactive materials and designing nuclear reactions for energy production or other purposes.
  • Studying the types and properties of emitted particles and radiation from cosmic sources helps us understand the composition and evolution of the universe.
Important concepts
  • Quantum mechanics: Governs the behaviour of particles at the subatomic level and explains the probabilities associated with various emission processes.
  • Energy levels: Electrons and other particles occupy specific energy levels within atoms. Transitions between these levels can lead to emissions.
  • Radioactive decay: Different types of radioactive decay involve different emitted particles and energy levels.
Natural causes of emissions
  • Stellar emissions: Stars like the Sun emit across the entire electromagnetic spectrum due to nuclear fusion at their core. This includes visible light, radio waves, infrared, ultraviolet, X-rays, and gamma rays.
  • Atmospheric phenomena: Lightning strikes emit electromagnetic radiation, including visible light and radio waves. Aurora borealis and australis (Northern and Southern Lights) produce colourful visible light emissions due to charged particles interacting with the atmosphere.
  • Forest fires and volcanic eruptions: These events release smoke, ash, and gases into the atmosphere. These particles scatter and absorb sunlight, impacting Earth’s energy balance. Volcanoes also emit various gases including sulfur dioxide and carbon dioxide.
  • Biological processes: Living organisms like plants and animals release gases during respiration and other metabolic processes. These include carbon dioxide, methane, and nitrous oxide, all greenhouse gases contributing to climate change.
Artificial Causes of Emissions
  • Fossil fuel combustion: Burning coal, oil, and natural gas for electricity generation, transportation, and industrial processes releases large amounts of greenhouse gases like carbon dioxide and nitrogen oxides, contributing significantly to climate change.
  • Industrial processes: Manufacturing industries release various pollutants, including volatile organic compounds (VOCs), sulfur oxides, and particulate matter, impacting air quality.
  • Agriculture: Fertilizer use, animal waste management, and agricultural land-use changes contribute to nitrous oxide emissions, a potent greenhouse gas.
  • Deforestation: Cutting down trees reduces the carbon sequestration capacity of forests, leading to increased atmospheric carbon dioxide levels.