Which Electromagnetic Wavelengths can Pass Through the Atmosphere?

Michael Anissimov
Michael Anissimov

The vast majority of electromagnetic radiation does not pass through Earth's atmosphere. Humans should be thankful for this, as if it did, life as it is known would not exist. Harmful X-rays, gamma rays, and ultraviolet light, most coming from the Sun, is largely absorbed in the upper atmosphere. Much infrared radiation is also absorbed by carbon dioxide and water vapor in the atmosphere. If it weren't, liquid water on the surface would be heated to the boiling point and evaporate, leaving a dry planet similar to Venus. Electromagnetic wavelengths above about 10 m (long-wavelength radio waves) are absorbed in the blanket of charged particles encircling the Earth, known as the ionosphere.

Visible light is umimpeded by the atmosphere.
Visible light is umimpeded by the atmosphere.

The most obvious category of wavelengths not absorbed by the atmosphere is visible light, with amplitudes between about 300 and 700 nm. Because these are one of the most prominent categories not absorbed by the atmosphere, because they are frequently generated by many common chemical reactions, and for many other reasons, it is only natural that organisms that evolved on the surface of the Earth have developed sensory organs well attuned to it.

A radio telescope looks at emissions from celestial bodies in the radio part of the electromagnetic spectrum.
A radio telescope looks at emissions from celestial bodies in the radio part of the electromagnetic spectrum.

At electromagnetic wavelengths shorter than violet, which ends at about 280 nm, atmospheric transmittance rapidly drops off to near-zero. Wavelengths longer than red, in the infrared portion of the spectrum, do make it through to some degree. They are also generated locally by anything that produces heat, and some organisms have evolved adaptations that allow limited infrared vision.

Visible light, which falls between ultraviolet light and infrared radiation, is an obvious example of a wavelength not absorbed by the atmopshere.
Visible light, which falls between ultraviolet light and infrared radiation, is an obvious example of a wavelength not absorbed by the atmopshere.

Radio waves with wavelengths between about 5 cm and 10 m easily make it through the atmosphere. This is why these waves are probably the third most-recognizable portion of the electromagnetic spectrum behind visible light and infrared. The atmosphere's transparency to waves permits the technology of radio, as well as sophisticated radio observatories that give researchers information about the universe. Astronomical observatories aiming for information about electromagnetic wavelengths blocked by the atmosphere either have to be floated on high-altitude balloons or put on satellites in orbit.

Many combat aircraft, including the Russian Su-25, are fitted with infrared arrays for the detection and tracking of enemy targets.
Many combat aircraft, including the Russian Su-25, are fitted with infrared arrays for the detection and tracking of enemy targets.
Michael Anissimov
Michael Anissimov

Michael is a longtime wiseGEEK contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

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