• 27 /July, 2018

Evolution of light bulbs over the years!

Light bulbs have seen an evolution over the years which has helped the human species in many more ways than we can imagine. From increasing the average workday to being a constant companion in the dark nights, light bulbs have been a driving force for everything we do.

Now, some people may argue that it is not the greatest invention of all the time but, it surely is one major invention that laid the stepping stone for many future inventions. Like all major inventions, the modern light bulb cannot be credited to any single inventor as it has seen a major transformation over the years.

 

How light bulb evolved- From Arc lamps to LEDs

The modern-day bulbs we ¬are not what people have been using traditionally. These light bulbs have gone under major changes to get to where it is now, that is, more efficient and environment-friendly. Let us now see how the light bulbs evolved over the years and why the previous bulbs were replaced with the advancement of technology.

 

Arc lamps- The first artificial light source

The arc lamp worked around the idea of generating an electrical spark through the air between two carbon rods. The gap between the rods must be of the right size to produce maximum light. If the gap is too large, the spark will flicker for a moment and then go out and if it is too small then the light produced would not be much.

The rods were made of carbon. The rod (carbon) is vaporized at high temperature (3600C). This high temperature ionizes the carbon vapour and normal air due to which light is produced. Carbon is used because the carbon vapour is highly luminous. An exchange of electron takes place between the ions of air and the carbon vapour. And the electric current passes from one electrode to the other.

But the arc lamps had certain disadvantages and therefore it was replaced later –

– The carbon rods had to be replaced after some time which required a person to do this job.

– It produced harmful UV rays.

– Created a constant buzzing sound if the light was produced.

– The longest rods lasted just about 75 hours.

– It emitted carbon monoxide gas which is very harmful.

 

Incandescent Bulbs light the way

Thomas A. Edison received a patent for the incandescent light bulb in 1879. Although there are many conspiracy theories suggesting that NikolaTesla invented the light bulb. Now, that is a different debate altogether but as far as we know, Edison gave us the incandescent light bulb. In 1835, there was the first sign of a constant electric light and after that, for 40 years scientists worked to develop what today we know as the incandescent light bulb.

The emission of light in an incandescent bulb is due to the heating of filament and contains an inert gas that helps to emit the light better. And a filament made of a rare metal called tungsten is also present in the bulb. This makes the light bulb more luminous, consumes less energy and the cost of making gets lower down.

Then came a filament made of a rare metal called Tungsten. This made the light bulbs more luminous, consumed less energy and the cost of making was lowered down.

Image Source : wikimedia.org

 

Halogen light bulbs- Improving the filament

Unlike the regular incandescent light bulb used earlier, a halogen (such as iodine or bromine) is used in the bulb. This improves the life of the Tungsten filament. Also, the illumination is better as the halogens have atoms distributed so the light produced covers a better distance.

A huge advantage of using halogens instead of inert gas is that when tungsten glows, it forms a residue which is wasted in an inert gas. Using halogens helps as the tungsten is redeposited to the filament after it cools down. This increases the life of the filament as it does not break down.

Image Source : www.edisontechcenter.org

 

CFLs – The Compact Florescent Lights

The Compact Florescent Lights, commonly known as CFLs, offer a considerable increase in the illumination as compared to Halogens Light bulbs and Incandescent Light Bulbs. Also, it takes 25% less energy.

It was the oil crisis of 1973 that forced the scientists to develop a lighting solution that consumes less energy. In 1976, Edward Hammer found a way to bend the florescent tubes which created the first CFL.

In a CFL, the current is passed through a tube that is bent and it contains Argon and a small amount of mercury vapour as well. The inside of the florescent tube is coated with phosphor. When an electric current is passed through the gasses, an invisible ultraviolet light is produced which further excites the phosphor which emits the visible white light.

With the coming of CFLs, also came the idea of coloured lighting. The florescent tubes that were used in the past were now made of different colours emitting the same white light but, the light that came out of the tube was of different colour due to the colouring of the tube.

Image Source : wikimedia.org

 

Light Emitting Diodes- The future is here

Light Emitting Diodes (LEDs) uses semiconductors (generally Gallium Arsenide) to emit light. Basically, LEDs are tiny bulbs that emit light in a single direction. Many tiny bulbs are fit together in a LED bulb to emit light.

LEDs don’t have a filament that gets hot and breaks after a certain amount of time; instead, they are illuminated by the movement of semiconductor electrons.

Semiconductors are a gem of the periodic table. They work as an insulator in the normal state but when they get excited, they work as a conductor.

Image Source : estore.finolex.com

So, this is the evolution of light bulbs over the years.

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