Natural light source

A natural light source is any source of light that occurs in nature without human intervention or creation. These sources can be celestial objects, atmospheric phenomena, or living organisms.

Celestial Objects
  • The Sun: Our primary source of natural light, providing warmth, driving photosynthesis, and allowing us to see.
  • Other Stars: Distant stars are inherently sources of light, though they appear far less bright to us due to their vast distances.
  • The Moon: It doesn’t produce its own light but reflects sunlight, providing a source of natural illumination at night.
Atmospheric Phenomena
  • Lightning: Electrical discharges in the atmosphere create bright flashes of natural light.
  • Auroras (Borealis and Australis): Caused by charged particles from the sun interacting with the Earth’s magnetic field, creating vibrant displays of light in the sky.
Living Organisms (Bioluminescence)
  • Fireflies: Use chemical reactions to generate light for attracting mates or prey.
  • Jellyfish: Some species emit light as a defence mechanism or method of communication.
  • Deep-sea creatures: Many creatures in the depths of the ocean produce light to navigate, lure prey, or find mates in a completely dark environment.
Key Points about Natural Light
  • Essential: Natural light is crucial for life on Earth, influencing plant growth, animal behaviour, and even human well-being.
  • Spectrum: Natural light sources often emit a broad spectrum of wavelengths, including colours visible to the human eye.
  • Unpredictable (sometimes): The availability and intensity of some natural light sources can be affected by factors such as weather, time of day, or season.
Light sources
Emission mechanism DescriptionExamples
LIGHT-EMITTING PROCESS
LuminescenceLight emission due to the excitation of electrons in a material.Electrons within a material gain energy and then release light as they return to a lower energy state.Bioelectroluminescence
Electroluminescence
Photoluminescence
- Fluorescence
- Phosphorescence
Sonoluminescence
Thermoluminescence
Blackbody radiation (Type of thermal radiation)Electromagnetic radiation (including visible light) emitted by any object with a temperature above absolute zero.Electromagnetic radiation (including visible light) emitted by any object with a temperature above absolute zero.All objects above temperature of absolute zero.
ChemiluminescenceLight from natural and artificial chemical reactions.Light from natural and artificial chemical reactions.Bioluminescence
Chemiluminescent reactions:
- Luminol reactions
- Ruthenium chemiluminescence
Nuclear reactionLight emission as a byproduct of nuclear reactions (fusion or fission).Light emitted as a byproduct of nuclear reactions.Nuclear reactors
Stars undergoing fusion
Thermal radiationLight emission due to the thermal excitation of atoms and molecules at high temperatures.Light emission due to the thermal excitation of atoms and molecules.Sun
Stars
Incandescent light bulbs
TriboluminescenceLight emission due to mechanical stress applied to a material.Light emission due to the mechanical stress applied to a material, causing the movement of electric charges and subsequent light emission.Sugar crystals cracking
Adhesive tape peeling
Quartz crystals fracturing.
Natural light source
Fireflies
Deep-sea creatures
Glowing mushrooms
Bioluminescence Light emission from biological organisms.Involves the luciferase enzyme.
Sun
Stars
Nuclear FusionLight emission as a byproduct of nuclear fusion reactions in stars.Electromagnetic spectrum (visible light, infrared, ultraviolet).
Fire
Candles
Thermal radiationLight emission due to the thermal excitation of atoms and molecules during the combustion of a fuel source.Burning of a fuel source, releasing heat and light.
Artificial light source
Fluorescent lights Highlighters
Safety vests
Chemiluminescence Light emission from chemical reactions.Fluorescence (absorption and re-emission of light).
Glow sticks
Emergency signs
ChemiluminescenceLight emission due to phosphorescence - a type of chemiluminescence.A type of chemiluminescence where light emission is delayed after the initial excitation.
Glow sticks
Light sticks
Chemiluminescence Chemiluminescence Light emission from a chemical reaction that does not involve combustion.
Tungsten light bulbs
Toasters
Thermal radiationHeated filament radiates light and heat.Light emission from a hot filament.
Fluorescent lamps
LED lights
ElectroluminescenceExcitation of atoms by electric current.Light emission when electric current excites atoms in a material.
Neon signsElectrical DischargeDischarge of electricity through gas.Light emission when electricity flows through a gas.
Sugar crystals cracking
Pressure-sensitive adhesives
TriboluminescenceLight emission from friction or pressure.Light emission due to mechanical forces.
Fluorescent paint Highlighters
Safety vests
PhotoluminescenceAbsorption and subsequent re-emission of light at a lower energy.Absorption and re-emission of light.

Light Sources: Mechanism, examples, and everyday applications

Footnote: Cerenkov radiation and Synchrotron radiation are not included in the table because they are not conventionally classified as light sources.