Our need for light
It's impossible to imagine modern life without electric light. So much of our working lives, our leisure time, and the running of our 24-hour-a-day cities, depends on a clean, safe supply of illumination.
But all this light is expensive to generate and uses a lot of energy. The traditional incandescent light bulb is a highly inefficient piece of technology, little changed from the original bulbs developed in the late nineteenth century.
Fortunately, scientists and engineers have come up with something that might be the solution.

21st Century Light

We take for granted how easy it is to switch on a light and pierce the gloom. The UN calls this a basic human right. But the technology most of us use dates back to the 1800s.Worldwide, a fifth of all the electricity we generate is used for lighting. Now this gives us a hefty energy bill – but it also means we pump out three times more carbon dioxide than the entire aviation industry.
And the need for light is only going to get bigger, as our populations grow, modernise and move into cities.
Living in darkness isn’t an option. But there’s a development that could slash our energy consumption.
The traditional light bulb is actually a pretty hopeless way of making light. It takes loads of electricity to generate just a little bit of brightness.
LEDs or light emitting diodes have been around since the sixties but people are getting really excited about them now.
Breakthroughs in their design means that LEDs are real contenders to replace the wasteful filament bulbs in most places. And as LEDs use a fraction of the energy to create light, this simple electronic component could have a global effect

How LEDs use quantum physics to shine
Incandescent light bulbs only convert 10% of their energy into light, with the rest lost as heat. LEDs generate light in a completely different way - but how? And why are they so much more efficient?
For over a hundred years, we’ve lit up our homes with incandescent light bulbs that work in a pretty simple way.
An electrical current goes through a thin wire tightly coiled inside the glass bulb. The current makes the wire get very hot and glow. And that gives off the light, but it’s pretty inefficient. 90% of the energy is lost as heat.
LEDs make light in a completely different way – and they use the curious world of quantum mechanics to do it.
Inside an LED are two layers of special material made from semiconductors. One layer contains a lot of energetic electrons. The other layer is filled with holes – which are really broken chemical bonds between atoms.
When an LED is hooked up to a battery, the electrons and holes flood towards the place where the two layers of the semiconductor meet. As soon as an electron meets a hole in this region, it falls into it, and repairs that chemical bond. In a flash, it releases the energy that it was using to move about – as a bright light.
And that keeps happening, as the battery keeps pushing electrons and holes towards each other.
Because most of the energy goes into making light rather than heat, LEDs are super-efficient.
And as new types of semiconductors are being developed, scientists are rapidly improving the efficiency of LEDs. In a few years, LEDs on the high street could be 10 times more than today

source:BBC I wonder

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