Chapter 15 Electromagentic Radiation

ultraviolet wave

Ultraviolet (UV) light has shorter wavelengths than visible light. Though these waves are invisible to the human eye, some insects, like bumblebees, can see them! Electromagnetic waves with wavelengths from about 400 billionths to 10 billionths of a meter

microwave

a form of electromagnetic radiation with wavelengths ranging from one meter to one millimeter; with frequencies between 300 MHz (100 cm) and 300 GHz (0.1 cm).

Global Positioning System (GPS)

a navigational system involving satellites and computers that can determine the latitude and longitude of a receiver on Earth by computing the time difference for signals from different satellites to reach the receiver. The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defense. GPS was originally intended for military applications, but in the 1980s, the government made the system available for civilian use.

cathode-ray tube

a sealed vacuum tube in which one or more beams of electrons are produced. A cathode ray tube (CRT) is a specialized vacuumtube in which images are produced when an electron beam strikes aphosphorescent surface. Most desktop computer displays make useof CRTs. The CRT in a computer display is similar to the"picture tube" in a television receiver.

visible light

a small portion of the entire electromagnetic spectrum. Visible light is a form of electromagnetic (EM) radiation, as are radio waves, infrared radiation, ultraviolet radiation, X-rays and microwaves. Generally, visible light is defined as the wavelengths that are visible to most human eyes.

radio wave

a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies from 3 THz to as low as 3 kHz, and corresponding wavelengths ranging from 100 micrometers (0.0039 in) to 100 kilometers (62 mi). Low-frequency electromagnetic waves with wavelengths longer than about 1 mm.

infrared wave

a type of electromagnetic radiation, as are radio waves, ultraviolet radiation, X-rays and microwaves. Infrared (IR) light is the part of the EM spectrum that people encounter most in everyday life, although much of it goes unnoticed. It is invisible to human eyes, but people can feel it as heat.

photon

energy depends on the frequency of the waves. A photon is an elementary particle, the quantum of all forms of electromagnetic radiation, including light. It is the force carrier for the electromagnetic force, even when static via virtual photons.

electromagnetic wave

made by vibrating electric charges and can travel through space where matter is not present Electromagnetic waves are waves which can travel through the vacuum of outer space. Mechanical waves, unlike electromagnetic waves, require the presence of a material medium in order to transport their energy from one location to another.

radiant energy

the energy of electromagnetic waves. The term is most commonly used in the fields of radiometry, solar energy, heating and lighting, but is also used less frequently in other fields (such as telecommunications). In radiometry, radiant energy is the energy of electromagnetic and gravitational radiation. The SI unit of radiant energy is the joule (J). The quantity of radiant energy may be calculated by integrating radiant flux (or power) with respect to time.

gamma ray

the most energetic form of electromagnetic radiation, with a very short wavelength of less than one-tenth of a nanometer. Gamma radiation is the product of radioactive atoms. Depending upon the ratio of neutrons to protons within its nucleus, an isotope of a particular element may be stable or unstable. Electromagnetic waves with wavelengths shorter than about 10 trillionths of a meter

carrier wave

the specific frequency of the electromagnetic wave that a radio station is assigned. A high-frequency electromagnetic wave modulated in amplitude or frequency to convey a signal.

transceiver

transmits one radio signal and receives another radio signal from a base unit. A transceiver is a device comprising both a transmitter and a receiver which are combined and share common circuitry or a single housing. When no circuitry is common between transmit and receive functions, the device is a transmitter-receiver. The term originated in the early 1920s.

X ray

very high frequency waves, and carry a lot of energy. They will pass through most substances, and this makes them useful in medicine and industry to see inside things. X-rays are given off by stars, and strongly by some types of nebula.Have wavelengths between about 10 billionths of a meter and 10 trillionths of a meter