## hpr3186 :: A light bulb moment, part 2

 A very brief history of lighting 
Natural light first came from fire
Then using oil and fat with a wick
Early candles used animal fat this smelled awful and tended to spit
Some parts of world used whole animals as candles
These early candles gave so little light that people generally just went to bed at sunset
Electric lighting started first by Humphry Davy in the early 1800’s using an arc, this was developed into commercial lighting in the 1840s
Arc lighting needed a complex mechanism to gradually push the contacts together as they burnt away
Gas lighting started around the 1850s this was improved in the 1870 with the advent of the Gas mantel.
Thomas Edison develop the electric light bulb in 1879 using a carbon filament. It took a great deal of effort to convince people to use it because gas lighting was so well established and worked well.
Many houses in Britain didn't install electric lighting until the 1930s
Finally electricity won as it could be used for so many other things.
The tungsten filament bulb
The filament within the bulb is made up of a tungsten coiled coil wire. This is done because the more compactly a filament can be wound the less heat is lost to the surroundings and the brighter the bulb will glow.
The tungsten halogen bulb
The next progression was tungsten halogen bulb, these bulbs are more efficient and give out twice as much light as ordinary bulbs and usually last twice as long.
All filament lights waste a lot of energy producing heat. An ordinary light bulb only gives out 10% of its energy as light, the rest is wasted as heat.
Fluorescent neon lights
Fluorescent neon lights were invented in 1905 by a French man called George Claude. These were used for advertising mainly in America.
Fluorescent strip light
The first fluorescent light was introduced in 1939 it uses the same principle as the neon light but incorporates a filament at both ends. It is filled with argon and mercury vapour. It mainly gives off ultra violet light the tube is coated on the inside with chemicals to convert the output to mostly visible light using a property called fluorescence.
Fluorescent tubes are four times as efficient as normal incandescent light bulbs and run cool.
The first energy efficient light bulbs were just fluorescent lights folded into a compact bulb shape.
Sodium lights
Sodium lights used mainly in street lighting are twice as efficient again as fluorescent bulbs they give off a rather horrible orange colour.
The first commercial high-pressure sodium lamps were available in 1965 from companies in the United States, the United Kingdom, and the Netherlands; at introduction a 400 watt lamp would produce around 100 lumens per watt https://en.wikipedia.org/wiki/Sodium-vapor_lamp
The next big development was LED lighting which I'll cover in my next episode.
