Babita has an electrical engineering degree and has taught engineering students and college students preparing for medical and dental college admissions tests.
What Are LEDs?
It's the holiday season and you're driving downtown to see strings of colorful lights strewn from lamp post to lamp post.
You take in the sight and admire the colors, wondering ''How do they make all those little bulbs in so many different colors?'' You remember hearing something about LEDs and decide to look them up when you get home.
So, what are these LEDs?
As the name suggests, light emitting diodes (LEDs) are diodes that emit light. Or, more specifically, LEDs are semiconductor electronic components that emit light. Let's take a minute to break that down.
What's a Semiconductor?
When a material conducts electricity, we call it a conductor, and when it does not allow the current to pass through, it's an insulator. We can engineer some materials to allow current to flow through only under certain conditions.
One way to do this is to add impurities into the material. Another is to change the temperature of the material. A material that has characteristics in between that of a conductor and an insulator is, fittingly, called a semiconductor.
These semiconducting materials are used to build electronics components for devices and appliances that we use daily.
What's a Diode?
How about a diode, then - what is it? A diode is a small electronic component used to build circuits, just like the ones in your phone or computer.
Diodes are very useful because they're made of semiconducting material, so we can control their behavior in the circuit. They also allow current to pass through in only one direction, which is great when designing circuits.
How Do Diodes Emit Light?
By definition, current is the flow of electrons. These electrons are negatively charged and high in energy. When an electron runs into a positively charged hole, the electron falls into the hole. When this happens, the electrons lose some of their energy in little packets of light energy called photons - this is the light that we see.
Depending on what semiconductor is used, these photons have different wavelengths. The wavelength of the light that is emitted determines the color we see.
There we have it! An LED is a light emitting diode that can convert electrical energy into light energy. By changing the semiconductor material from which the LED is made, we can change the color of the light emitted. That's how we make LEDs of different colors.
How Are LEDs Used?
Because LEDs are inexpensive, they have many applications, including in lighting and electronic/medical devices.
Compared to the regular Edison incandescent bulbs, LED bulbs have lower maintenance costs, last longer, and use less power, so more and more homes are switching to LED bulbs these days. High-power LED bulbs are also used in industries for brightly lighting large warehouses and workspaces.
Lights from LEDs are also used in many other ways:
- Electronic appliances show their operating modes using LEDs. Next time you turn on a TV, notice the green light that comes on to indicate that the power is on - that's an LED.
- The traffic lights at intersections use arrays of green, orange, and red LEDs.
- The floor lighting inside places like movie theaters and airplanes are also LEDs. Check for those when you are at the movies next time.
- Many new flashlights use LEDs because they give out bright, white light.
Bili light is a medical device used in neonatal care units to provide light therapy to newborn babies, especially those born prematurely. These babies are not yet able to break down a compound called bilirubin, which is produced in the liver. This is why some babies have yellow skin or jaundice.
Blue lights at certain wavelengths have the ability to break down bilirubin, so medical devices made of blue LEDs are used to treat jaundice in premature babies.
A light emitting diode (LED) is a semiconductor electronic device, called a diode, that has the special property of emitting light. Depending on which semiconductor is used, we can change the color of the light produced by the LED. Because of this property, today we use LEDs for many different applications:
- Household light bulbs
- Industrial-use lightings
- Operating indicators on electronic devices, such as a TV
- Traffic lights that use green, orange, and red LEDs
- Floor lighting in movie theaters and airplanes
- Flashlights that give out bright white light
- Bili lights for treating neonatal jaundice
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