OUR ATTEMPTS TO TURN NIGHT INTO DAY

Here, let us explore various sources of light.
A point to remember;
Normally, there are two processes which yield light.
1. When the charges vibrate(ions, electrons) light waves[electromagnetic waves] are emitted
2. When high energy electrons return to the low energy state, the excess energy is released as light.
But, in this article, we will simply say, when the atoms are agitated, light is given out.

1. Oil lamps and candles:
Here, oil and wax burn using atmospheric oxygen. It is a combustion process. Heat generated in the process agitates the vapour atoms around the wick. Hence light is emitted.

2. Incandescent lamps:
The tungsten bulb is the first electric lamp. Electric current is sent through the tungsten filament; Heated to very high temperature; tungsten atoms are agitated and emit light. A bulb surrounds the filament to keep away the oxygen. Hence, no burning here. It is the first incandescent lamp.

3. Fluorescent lamp:
A long tube or folded tube is filled with mercury. When electric power is given, the mercury is vapourised and the electric current (electrons) passes through it. The electrons collide with mercury atoms (agitation) which yields visible and ultraviolet light. The UV light is turned into visible light by the fluorescent coating on the walls of the tube. Hence the name fluorescent lamp.

Sodium, Neon, Mercury lamps:
Here, electric current pass through sodium, neon, mercury or argon vapours. The atoms are agitated and excited. Hence they give out the light of characteristic colours.

LED lamp:
In a diode, electron rich and electron starving materials are joined together. When the electron goes from the rich side to the poor side, light is emitted. Technically, we can say, the excited (high energy) electrons from one side go and relax (low energy) on the other side. The excess energy is released as light. It is the LED -light emitting diode.
Today LEDs are everywhere. (mobile, TV, computer, signal, all lamps)
The future seems to have arrived. Tomorrow, wallpaper, with embedded LEDs may glow. We need not have separate lamps.

SUN:
The sun, powerful and natural source of light. Atomic fusion takes place continuously in the sun. Heat energy is released in this fusion. This energy agitates the solar atmosphere molecules which emit visible light.
Our eyes have evolved to sense the sunlight. Hence the artificial lights must be similar to the sunlight. But artificial sources never match the sun.
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