Science 3-3 Producing Visible Light

But often, lights that contain different gases or a mixture of gases are also called ____. Different gases produce different colors of light. Sometimes colored glass tubes are used to produce other colors.

neon lights

What is a neon light?

A sealed glass tube that contains neon gas.

What are neon lights commonly used for?

Bright, flashy signs.

What is a fluorescent light and how do they work?

A bulb that contains a gas and is coated in the inside with powder. When an electric current passes through the bulb, it causes the gas inside to give off ultraviolet rays. When the ultraviolet rays hit the powder in the tube, the powder gives off visible light. Fluorescent lights give off most of their energy as visible light and only a little energy as infrared rays. Therefore, fluorescent lights do not get as hot as incandescent light bulbs.

What is a vapor light?

A bulb that contains neon or argon gas and a small amount of solid sodium or mercury is a vapor light.

What are Tungsten-Halogen Bulbs?

A bulb that has a tungsten filament and contains a halogen gas such as iodine or bromine is called a tungsten-halogen bulb.

What is an incandescent light?

A light bulb that glows when a filament inside it gets white hot.

What color does argon gas and mercury vapor produce?

Greenish blue light

How do you know if an object is luminous? What are some examples?

If it gives off its own light. Examples are light bulbs, the sun, and burning logs.

How do you know if an object is illuminated? What are some examples?

If you see it by reflected light. (This is why you can see your notebook in front of you.) Ex. the moon, notebook and desk

Different types of light bulbs may be used to illuminate the spaces around you. What are the most common types of light bulbs?

Incandescent, tungsten-halogen, fluorescent, vapor, and neon lights.

What are LEDs and how do they work?

Light emitting diodes, commonly called LEDs, are found in all kinds of devices. Basically, LEDs are just tiny light bulbs that fit easily into an electrical circuit. But unlike ordinary incandescent bulbs, they don't have a filament that will burn out, and they don't get especially hot. They are illuminated solely by the movement of electrons in a semiconductor material, and they last just as long as a standard transistor. The lifespan of an LED surpasses the short life of an incandescent bulb by thousands of hours.

How do you see light?

Most light you see are visible because they reflect light from some kind of light source.

Where could neon lights be located?

Neon lights are often used to attract attention to stores and theatres.

What color does krypton produce?

Pale violet light

What color does helium produce?

Pink light

What color does a true neon light give off?

Red light

What is a spectroscope?

Some light bulbs produce a continuous spectrum of all the wavelengths of visible light. Others produce only a few wavelengths. You can use an instrument called a spectroscope to view the different colors of light produced by a light bulb.

Where could vapor lights be located?

Streets and parking lots may be lit with vapor lights.

Why are tungsten-halogen bulbs more efficient than ordinary bulbs? Why?

The filament of this bulb gets much hotter than in an ordinary light bulb, so the bulb looks whiter. Tungsten-halogen bulbs are more efficient than ordinary bulbs because they give off more light and use less electrical energy. But they do also give off more heat. Because tungsten-halogen bulbs get so hot, they must be kept away from materials that could catch fire.

Are ordinary light bulbs efficient? Why?

They are not efficient. Less than 10 percent of their energy is given off as light. Most of their energy is given off as infrared rays, which is why they get so hot.

How does ordinary light bulbs work?

They have a thin wire called the filament. It is made of a metal called tungsten. When an electric current passes through the filament, it quickly heats up and becomes hot, giving off white light. The filament is enclosed in an airtight glass bulb. Most ordinary light bulbs contain small amounts of nitrogen and argon gases.

Are vapor lights efficient? Why?

They require very little electrical energy to give off a great deal of light, so they are quite efficient.

Are fluorescent lights efficient? Why?

They usually last longer than incandescent lights and use less electrical energy for the same brightness. So, fluorescent lights are very efficient.

Who created the first light bulb?

Thomas Edison, the American inventor, patented the first practical incandescent light bulb in 1879.

How does a vapor light work?

When an electrical current passes through the gas, the gas heats up. The hot gas then heats the sodium or mercury. The heating causes the sodium or mercury to change from a solid into a gas. In a sodium vapor light, the particles of sodium gas glow to give up a yellowish light. A mercury vapor produces a bluish light. Both sodium and mercury vapor lights are used for street lighting in parking lots.

How is a neon light lit?

When an electrical current passes through the neon, particles of the gas absorb energy. However, the gas particles cannot hold the energy for very long. The energy is released in the form of light. This process is called electric discharge through gases.