Chapter 13 Section 3

Types of Light Incandescent—a typical light bulb. It is made by heating a piece of wire until it glows.

Fluorescent—a light that uses phosphors to convert ultraviolet radiation to visible light. They use about 1/5 the amount of energy of an incandescent light, and last longer. They are filled with a gas, and the inside is coated with phosphors. Energy is emitted through the bulb and the electrons get excited enough to start producing ultraviolet radiation inside the light bulb. This cause the phosphors to begin to glow and produce visible light.

Neon—similar to fluorescent lights Neon—similar to fluorescent lights. Electrons still flow through a tube, but the collisions make the visible light. The different colors depend on the types of as used. Neon gas usually makes a red or orange light. Argon is used to make purple. Argon mixed with mercury produces blue.

Sodium-Vapor—these are what are used in street lamps and other outdoor lighting. It usually appears yellow.

Tungsten-Halogen—used to create high intensity bright lights Tungsten-Halogen—used to create high intensity bright lights. It uses a halogen gas and a tungsten wire to light up. Used in movie sets and in underwater photography.

Lasers A laser starts with a light producing material wrapped in an energy source. The light given off by this is reflected between two mirrors that eventually get the light to have the same wavelength. Can be made of solids, liquids, or gases; but the most common is the helium-neon laser, which produces a red beam of light.

Coherent vs incoherent Coherent—is when the crests and troughs line up perfectly. This is the type of light you need for a laser, because the light will not disperse. Incoherent—contains more than one wavelength that are not aligned. This would be like a typical light bulb where the light is dispersed. How lasers work

Uses of lasers Compact discs– plastic discs with reflective surfaces used to store data in digital form. A laser is used to read the disk. It emits a light beam that then bounces off the disk and hits a detector. The detector then decodes the disk and allows it to reform an image or sound.

Medical uses—we use them to remove cataracts, reshape the cornea, repair the retina, remove small tumors and birthmarks, etc.

Content Check What is an example of an incandescent light bulb? Why does it get hot? What causes the color in a neon light? How doe mirrors help in creating a laser beam? What are some of the uses of lasers?