Sources of Light

Light is not simply something we turn on and off; it's the reason we're able to see, plant crops, and even use technology. From the heat of the sun to a burning candle's glow, light sources in the world around us mould our day-to-day life and natural world. Knowledge of the various light sources, including natural and artificial sources of light, is central to understanding how light sustains life and powers ecosystems.

1.0Understanding the Basics: Introduction to Light

Light is a form of energy that enables us to see. It is an electromagnetic wave that propagates in a straight line without any medium. The velocity of light in a vacuum is about 3 × 10⁸ meters per second (m/s). Light makes it possible for us to see the world around us by reflecting from surfaces and passing into our eyes. It is also responsible for the growth of plants, controlling sleeping patterns, and energising devices such as solar panels.

2.0What are the Sources of Light?

A light source is any object that produces light. There are objects that produce light naturally, and there are others that need a power source from outside. Sources are classified into luminous (self-emitting light) and non-luminous (can only be seen when lit by other sources). 

3.0Different Types of Light Sources

Light sources can be classified into two broad categories, each of which is important in maintaining environmental balance and supporting human activities. The differentiation is based on the origin of the light, which includes: 

A. Natural Light Sources

Natural sources of light are those that occur naturally without intervention from human beings. Natural light sources are crucial for sustaining life and also regulating day-night cycles on Earth. The objects producing their own light are also known as Luminous objects. Some examples of light sources of this type include: 

• Sun: The most important natural source, supplying heat and light necessary for survival.
• Stars: Stars are the suns that are far away from our solar system, which shine by emitting their own light.
• Fire: A natural source of light created through the burning of materials.
• Lightning: An intense but short burst of light resulting from electrical discharge in storms inside the clouds. 
• Bioluminescent Organisms: Certain animals, such as fireflies, deep-sea jellyfish, and fungi, also emit light biologically.

B. Artificial Sources of Light

Artificial sources of light are man-made light sources. When natural light is not sufficient to illuminate the entire surroundings, artificial sources of light are used. These human-made appliances or sources of light depend on electricity, chemical reactions, or combustion to work properly. The objects used as artificial sources of light are also known as non-luminous objects. Examples of light sources of this type include: 

1. Electric Bulbs: Electric bulbs, as the name suggests, use electricity to generate light through a glowing filament.
2. LEDs (Light Emitting Diodes): LEDs are very efficient light sources applied in homes, devices, and automobiles.
3. CFLs (Compact Fluorescent Lamps): These are a kind of power-saving bulbs that release light through the excitation of gas within the tube.
4. Candles and Oil Lamps: Candles and oil lamps are the oldest and classic sources of light, working on the principle of combustion.
5. Flashlights: These are portable devices powered by batteries that are handy in times of emergency, when there is a power cut or when stranded in the way.
6. Street Lights: Street lights are light sources that are placed on roads to provide nighttime visibility to passengers and drivers.

4.0Importance of Light Sources

Light is everywhere, and so are light sources. These sources hold a major impact on humans, nature, and technology. Let’s explore some major importance of light sources in this section:  

In Nature

• Light aids photosynthesis in plants, which allows them to make food and give off oxygen. The sun is a major light source, which supports this process of photosynthesis. 
• Light also assists in controlling the biological clock of humans and animals (circadian rhythm).
• It is the major source of heat; hence, it provides warmth, which is necessary to survive in the majority of ecosystems and weather. 

In Human Life

• Everything we see around us and determine the colour of each object is possible only due to the effect of light. The spectrum of visible light and the reflection and scattering of this light help us do so. 
• Artificial light has prolonged work hours, which ultimately enhances lifestyle and security.
• The dual nature of light has helped humans apply it in communication systems such as fibre optics.
• Light has also found its way into healthcare and medicine. For example, in laser surgery, X-rays, and phototherapy, all these technologies use light to get a scan of the internal organs of the body.
• Road accidents are reduced by streetlights and car headlights.
• Light is applied in alarm systems and warning signs to promote safety.

5.0Bioluminescence — Nature’s Magical Glow

Bioluminescence is a beautiful phenomenon of the production and emission of light by living organisms; the term bio in the word Bioluminescence itself means life. This emission and production is possible via chemical reactions that occur within their own bodies. This chemical reaction includes the reaction of a light-emitting molecule called luciferin with oxygen in the presence of an enzyme called luciferase. Note that, unlike artificial light, bioluminescent light is cold light, meaning it produces light but not heat. 

Bioluminescence is mainly found in deep-sea creatures, such as jellyfish, anglerfish, insects (with one of the famous light-emitting insects being fireflies), fungi, and marine plankton that light up the ocean at night.