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How Light Works

Apr 08, 2014 | by Wendy Weinert

How Light Works

Light is simply amazing. It is ever present, sustaining life, warming our planet, lighting our homes, and it's something most of us take for granted. It is undeniably one of the fundamental cornerstones of life; from photosynthesis to solar electricity, light is what continues to preserve life and drive progress on this planet. Scientists will tell you that light is a wave of electromagnetic energy that travels through space. But very simply put, light is nature's way of transferring energy quickly and efficiently. Even more simply, light is energy.

Light is generally thought to exist as both particles and waves, which means it has a sort of double nature. As a particle, light is comprised of small clusters of energy called photons. Some photons have more or less energy than others, which leads to ranges of different types of light. Light is also a wave, which is a little more difficult to describe, but think of it this way: If you take a string and tie it to a pole and flick it up and down, you will create a series of waves. Now, depending on how quickly you perform this action (how much energy you put in), the waves will be further apart and rounder or closer together and more sharply defined. It's the same way with light: Light waves have a range of high and low frequencies, and each gives off certain kinds of energy, including the type of light that we can see, which is in the visible light spectrum.

We all remember Roy G. Biv from school: He's a representation of the visible light spectrum. Depending on the frequency of the wavelength, the color that we see is different. Higher-frequency visible light waves are violet, and lower frequency wavelengths look red; between the two is the rest of the visible light color spectrum. Additionally, there are wavelengths of light that we can't see - they are found on the extreme ends of the spectrum. Below the visible red light, there is infrared light, and above visible violet light is ultraviolet light. Each require special equipment to be able to be seen by human eyes, but they are ever present all around us in both our daily lives and technology. Infrared light is useful in a number of technologies, including wireless phones, TV remotes, and special kinds of camera equipment and film. When you go to the beach and slap on the sunscreen, you are trying to protect yourself from UV (ultraviolet) rays that come from the sun, and while UV rays are used in a variety of technologies in the medical field, prolonged exposure to UV rays without proper safety can have detrimental effects on your health.

Human beings, not being content with just sunlight, sought to be able to capture light and generate it themselves. Enter Thomas Edison. This well-known inventor was the first to create the first electric light bulb, known as an incandescent light bulb. Incandescent light bulbs generate light by utilizing heat from electrical current. When this current passes through a wire, the wire coil inside the light bulb (also called a filament) becomes so hot that it gives off light. Filaments are normally made with a metal called tungsten. To keep it from burning up immediately, the filament must be sealed in an air-tight bulb or have the bulb space filled with gas that will keep it from burning. It takes a significant amount of energy in order to sustain the glow, and the heat eventually causes the filament to go bad. Recently, the use of fluorescent light bulbs has become very common due to the fact that they use much less energy, provide better light, and last much longer than incandescent light bulbs. Fluorescent light bulbs are pretty much just glass tubes filled with some argon gas and a little mercury. When electrical current travels through this type of bulb, the gas picks up the electrical energy and radiates it back as ultraviolet light. The ultraviolet light then activates the inner part of the tube, which is coated with a phosphor, a substance that glows when exposed to UV light.

Through scientific innovation, human beings have become capable of creating light and even repurposing it to aid progress in other areas. Our study of light has given us incredible medical innovations, like X-rays and phototherapy, and advancements in light technology have given us precise lasers and brighter, more crisp images in both cameras and television. We depend upon it much more than we realize, which is why having a good understanding of what light is and how it works is such valuable knowledge.

To learn even more about how light works, check out some additional information here:

The Basics of Light: This general article that covers the basic description of light and its characteristics.

Sources of Visible Light: Florida State University provides an informative explaining what visible light is and a guide to determining which wavelengths of light are which perceived color.

Wave Behaviors: NASA discusses how light waves behave when reflected, refracted, transmitted, and absorbed.

What is Infrared Light?: This brief scientific description discusses invisible infrared light wavelengths.

An Introduction to Infrared Technology: University of Wisconsin researchers detail the application and uses of infrared wavelength technology.

Ultraviolet Light: This article defines what ultraviolet light is and discusses its purpose in astronomy and other scientific fields.

Hazards of Ultraviolet Light: The University of Washington gives an in-depth discussion of the hazards of ultraviolet light and how to safely utilize it.

Why Does Ultraviolet Light Cause Color to Fade? This Library of Congress article explains photodegredation, the common fading that occurs when textiles have been exposed to sunlight for an extended period of time.

How Does a Light Bulb Work?: Michigan State University describes how an incandescent light bulb works.

Diagram of an Incandescent Light Bulb: This diagram shows the parts of an incandescent light bulb.

After You Hit the Switch: How Lights Work: Northwestern University outlines the variety of lights and light bulb options available to the average consumer.

The Unique Health Effects of Blue Light: Researchers have found that blue light can help reset the body's circadian rhythm.

Producing Light: A Union College article discusses how light can be produced.

Incandescent Lamps: This page gives a history of the incandescent light bulb, from inception through a variety of adjustments and improvements that gave us the modern incandescent light.

Fluorescent Light Bulbs: The very popular fluorescent light bulb is expected to replace incandescent light bulbs in the near future.

Disposing of Fluorescent Bulbs: Fluorescent bulbs have specific disposal requirements; this site outlines why and how to recycle them.

Pros and Cons of Various Lightbulbs: Different types of light bulbs have different advantages and disadvantages.

Laser and Laser System Classification: Arizona State University provides an informative guide to laser classifications and hazards.

What to Do if a Fluorescent Bulb Breaks in Your Home (PDF): In case of breakage, this PDF is a guide to helping you safely clean up a fluorescent bulb.

The Exploratorium: Science Snacks About Light: This page suggests kid-friendly experiments you can do to learn about light.