Electromagnetic radiation

Electromagnetic radiation is a propagating wave in space with electric and magnetic components. These components oscillate at right angles to each other and to the direction of propagation.

Electromagnetic spectrum

Generally, EM radiation is classified by wavelength into electrical energy, radio, microwave, infrared, the visible region we perceive as light, ultraviolet, X-rays and gamma rays.

Related Topics:
Electrical energy - Radio - Microwave - Infrared - Visible region - Ultraviolet - X-ray - Gamma rays

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The behavior of EM radiation depends on its wavelength. Higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths. When EM radiation interacts with single atoms and molecules, its behavior depends on the amount of energy per quantum it carries.

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Spectroscopy can detect a much wider region of the EM spectrum than the visible range of 400 nm to 700 nm. A common laboratory spectroscope can detect wavelengths from 2 nm to 2500 nm. More in-depth information about the physical properties of objects, gases, or even stars can be obtained from this type of device. It is widely used in astrophysics. For example, many hydrogen atoms emit radio waves which have a wavelength of 21.12 cm.

Related Topics:
Spectroscopy - Astrophysics - Hydrogen - Atom - Emit - Radio wave - Wavelength - Cm

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Light

EM radiation with a wavelength between 400 nm and 700 nm is detected by the human eye and perceived as visible light.

Related Topics:
Wavelength - Nm - Human - Eye - Light

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If radiation having a frequency in the visible region of the EM spectrum shines on an object, say a bowl of fruit, this results in our visual perception identifying information from the scene. Our brain's visual system processes the multitude of reflected frequencies into different shades and hues, and through this not-entirely-explained "psychophysical phenomenon," most humans perceive a bowl of fruit.

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In the vast majority of cases, however, the information carried by light is not directly apprehensible by human senses. Natural sources produce EM radiations across the spectrum; so, too, can human technology manipulate a broad range of wavelengths. Optical fiber transmits light which, although not suitable for direct viewing, can carry data. Those data can be translated into sound or even into an image. The coded form of such data is similar to that used with radio waves.

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Radio waves

Radio waves carry information by varying amplitude and by varying frequency within a frequency band.

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When EM radiation impinges upon a conductor, it couples to the conductor, travels along it, and induces an electric current on the surface of that conductor by exciting the electrons of the conducting material. This effect (the skin effect) is used in antennas. EM radiation may also cause certain molecules to absorb energy and thus to heat up; this is exploited in microwave ovens.

Related Topics:
Conductor - Induces - Skin effect - Microwave oven

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