What Is the Electromagnetic Spectrum?

Everywhere you look, you are surrounded by the electromagnetic (EM) spectrum. The EM spectrum encompasses all frequencies of radiation bathing our planet and spans a range of wavelengths, from long radio waves to short gamma rays.

Radio Frequency

The portion of the EM spectrum with the longest wavelength is radio frequency (RF.) Nearly all radio equipment will utilize an RF directional coupler to detect radio waves and calculate the power produced. RF applications include GPS, cell phones and radio astronomy.


Aside from a fast way to prepare dinner, microwave radiation is often used in astronomy to map parts of the universe that are otherwise invisible to the human eye. Microwaves are also used in medicine as a form of therapeutic muscle relaxation called microwave diathermy.

Infrared Frequency

The human body emits radiation in the infrared portion of the EM spectrum and can be seen using night-vision goggles. The dark sections of the Milky Way galaxy that obscure starlight are created by dust that astronomers study with infrared-sensing equipment.

Visible Light

The human eye is designed to detect light in this narrow band of radiation, thus allowing us to see our world clearly. Relatively little astronomy is done in the visible light spectrum since more complex, intriguing phenomena occur in other bandwidths, such as radio or x-ray.

Ultraviolet Light

The ultraviolet (UV) radiation from the sun is responsible for tanning and burning. UV radiation can also be used to sterilize medical equipment. Stars known as blue giants and white dwarfs are studied in the UV spectrum.

X-Rays and Gamma Rays

The shortest wavelengths of the EM spectrum are x-rays and gamma rays. These high-energy particles are emitted from astronomical objects such as black holes and supernovae.

From cell phones to dental x-rays, the EM spectrum encompasses a large range of energetic wavelengths that we use every day.

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