Various Types of Electromagnetic Radiation

Description: Radio waves are electromagnetic waves that range from a frequency of about 3 hertz and a wavelength on the order of magnitude of 100,000 kilometers to a frequency of about 300 gigahertz and a wavelength on the order of magnitude of 1 millimeter.

Uses: Radio waves are used by humans for the wireless transmission of sound messages or other information. Radio waves that originate from outer space are studied by astronomers to gather information about the universe.

Facts: Information is placed in a radio wave in one of three basic ways: Amplitude modulation (AM), in which the intensity of the wave is varied, frequency modulation (FM), in which the frequency of the wave is varied, or in digital form, also known as pulse modulation, in which the signal is rapidly turned on and off in a defined pattern.

Radio frequencies can be divided into types and uses based on frequency ranges. For example, VHF (very high frequency) radio waves are used for FM radio and television, and SLF (super low frequency) waves are used to communicate with submarines underwater.

Description: Microwaves are electromagnetic waves that range from a frequency of about 1 gigahertz and a wavelength on the order of 30 cm to a frequency of about 300 gigahertz and a wavelength on the order of 1 mm. This range of frequencies overlaps with the shorter radio waves.

Uses: Microwaves are often used to carry broadband telegraphy signals (telephone and television) between stations on the Earth as well as between Earth stations and communications satellites. Microwaves are also used to communicate with space probes.

Microwaves are also commonly used for heating and cooking food. They are absorbed by water and fats and thus heat food from within.

Facts:

• Microwave transmitters and receivers are parabolic dish antennas.
• Microwaves are used for radar systems, which are used to track the position and speed of various objects.
• Microwaves are commonly generated by devices known as the klystron (primarily used for communications applications) and the magnetron (primarily used for radar and microwave ovens). Solid state devices such as the Gunn diode and the tunnel (or Esaki) diode, as well as the maser (an acronym for "microwave amplification by stimulated emission of radiation") are also used to generate microwave radiation.

Also known as: Heat

Description: Infrared radiation consists of electromagnetic waves that range from a frequency of about 10¹² and a wavelength on the order of 1 mm to a frequency of about 5 x 10¹⁴ Hz and a wavelength on the order of 750 nm. Invisible to the naked eye, infrared radiation can be detected as warmth by the skin.

Uses: The detection of infrared radiation is used in a wide array of applications, including night vision instruments, thermography, telecommunications, and meteorology.

Also known as: Light

Description: Visible radiation consists of electromagnetic waves that range from a frequency of about 429,000 gigahertz and a wavelength on the order of 7 x 10^-5 (red) to a frequency of about 750,000 gigahertz and a wavelength on the order of 4 x 10^-5 (violet). This type of electromagnetic radiation is visible to the human eye and consists of a continuous spectrum of colors including red, orange, yellow, green, blue, and violet.

Facts: About one half of the Sun's energy is released as visible light, which is at the peak of the Sun's emission spectrum. Visible light is essential for photosynthesis. Fossil fuels like coal and oil are formed from accumulations of plant material created by photosynthesis.

Also known as: UV

Description: Ultraviolet radiation consists of electromagnetic waves that are shorter than visible light waves and longer than x-rays, with a wavelength ranging from about 400 nanometers [and a frequency of about 750,000 gigahertz] for near ultraviolet (near to the visible color violet) to one nanometer (extreme deep ultraviolet) [with a frequency of about 30,000,000 gigahertz].

Facts: Mercury and xenon arc lamps produce ultraviolet radiation. Fluorescent light bulbs produce short-wave ultraviolet radiation that excites phosphors on the inside coating of the bulb to produce visible light.

Ultraviolet radiation can be detected by photographic plates.

Near-ultraviolet light is invisible to the human eye. However, many insects can see it and flowers can exhibit colorings in the ultraviolet portion of the spectrum.

Ultraviolet light (and higher frequency electromagnetic radiation) has enough energy to ionize atoms and molecules that it comes into contact with. This changes the atoms and molecules by knocking electrons away, which is potentially damaging to living tissue. Ultraviolet radiation is what causes skin to tan. This energy does not penetrate into the human body much below the skin, but can cause sun burns and more severe damage with more exposure leading to skin cancer, eye cataracts, and damage to the body's immune system. The ozone layer in the atmosphere provides natural protection from the most harmful ultraviolet radiation emitted by the Sun.

Description: X rays consist of electromagnetic waves that are shorter than ultraviolet waves, with wavelengths of ten nanometers and smaller and frequencies of 30,000,000 gigahertz and greater. X rays are so small that their radiation can be generated within single atoms.

Uses: X rays are well known for their ability to generate images of the inside of the human body. They are often used to create images of bones and tissues within the body.

Facts: X rays are often produced in X ray tubes by the deceleration of energetic electrons as they hit a metal target.

X rays have the ability to ionize atoms and molecules. Since they can penetrate the human body, they are a health hazard. Large doses of X rays may lead to cancer and birth defects.

There are very strong X ray sources in deep space, such as from certain double star sources where one star is a compact neutron star or a black hole.

Description: Gamma rays are a type of electromagnetic radiation with very high energy formed from the nuclei of atoms as a part of a radioactive process. Photons generated from gamma rays may be identical to X rays, but are not generated the same way. Gamma rays typically have frequencies greater than 100 billion gigahertz (10²⁰ hertz) and wavelengths less than 0.001 nanometers (10^-12 meters).

Uses: Gamma radiation is sometimes used to sterilize medical instruments and supplies that cannot be boiled.

Facts: Gamma rays are between 10,000 and 10,000,000 times more energetic than electromagnetic radiation in the form of visible light.

Gamma rays have great penetrating power and can readily damage biological organisms. Gamma rays penetrate substances deeply because they do not carry an electrical charge that would interact with matter and slow them down more quickly.

Radon gas generates gamma rays, which is why radon is hazardous when it escapes the ground and enters the basements of buildings.