Electromagnetic Spectrum: The Complete Guide

visible light with wavelength difference

Electromagnetic Spectrum: The Complete Guide

In September 2019, Elon Musk began launching a massive internet constellation into Lower Earth Orbit. The 42,000-satellite program Starlink intends to connect people in some of the remote places around the world. 

These internet satellites function on the 12 GHz waveband, a portion of the electromagnetic spectrum that quickly sends information from space. However, this is only one way we use light waves daily. Continue reading to learn more about the electromagnetic spectrum and how it’s applied today.

What Is the Electromagnetic Spectrum?

Vector diagram with the visible light spectrum
EM spectrum is the entire range of light radiation, which is the energy that spreads from an object.

Whether sending a text message or traveling through airport security, the technology that enables it utilizes the electromagnetic (EM) spectrum. Everything emits radiation, but their waves vary widely. The electromagnetic spectrum is so broad that humans can only see. 

How Is EM Radiation Measured?

When electromagnetic researchers work with various data, they typically use three types of units. They do this because the range of waves along the spectrum is so wide that some units are easier to use than others. The units below typically describe electromagnetic radiation:

  • Frequency
  • Wavelength
  • Energy


Scientists use frequency to describe how many cycles a wave emits within a specific time. The measurement for frequency is Hertz (Hz), which represents one cycle per second. This property is often used to measure electromagnetic waves on the longer end of the spectrum.


As waves start to get smaller in their cycles, EM researchers start to use wavelength more often. This unit measures the length of a cycle, often done in meters. Scientists use wavelengths to measure visible light but it can get as small as 10-8 centimeters (angstroms).


Because electromagnetic radiation gets incredibly small near the end of the spectrum, scientists prefer to describe them regarding their energy output. Electron volts (eV), which measure the waves at the shorter end of the spectrum, describe the change in potential energy that it experiences from its starting position to a constant distance.

Portions of the Electromagnetic Spectrum

Electromagnetic researchers break up the vast range of the spectrum into portions to make it easier to categorize their properties. While there is no hard line that defines them, scientists use seven portions to separate the spectrum, which include:

  • Radio waves
  • Microwaves
  • Infrared light
  • Visible light
  • Ultraviolet radiation
  • X-rays
  • Gamma rays

Let’s look at each one in more depth.

Radio Waves

These are the first portion of the spectrum and makeup all the radiation up to about 30GHz, making it one of the largest. Frequency is the common standard for measuring radiowaves, but it might also use wavelength in some cases. The lower frequency of radio waves makes them ideal for communicating across long distances, such as with orbital satellites.


Depiction of the Cosmic Microwave Background Radiation (CMBR)
Scientists use large dish antenna to study microwaves emitted by stars, planets, galaxies, and nebulas.

The second portion of the spectrum continues to use frequency in its long waves but also introduces wavelengths at its shorter end. Microwaves start to enter the terahertz range, yet their wavelength might only reach a meter at its widest. Its energy is great enough to travel through cloud cover, making them useful for applications such as GPS and weather tracking.

Infrared Light

The infrared spectrum sits between microwaves and visible light and features wavelengths from about .7 micrometers and 1000 micrometers. Infrared is good at traveling through dense cloud cover, making them ideal for capturing data on celestial bodies hiding behind space dust. On earth, this spectrum is used with night vision goggles, which pick up trace heat levels from our bodies.

Visible Light

Any form of light we can see, from the lamp on our desk to the campfire in our backyard, lets off visible light. This is the range of electromagnetic radiation we can see with our unaided eyes, measuring from about 400 to 700 nanometers. When visible light reflects off an object, its wavelength gives it its color. The color spectrum of visible light ranges from red (700nm) to violet (400nm).

Ultraviolet Radiation

As wavelengths start to get extremely small, the amount of energy they produce can get intense. Ultraviolet radiation measures around 10 to 380 nanometers, and some researchers use eVs at the shorter end of the portion. The ultra-frequent UV waves that emit from the sun can cause sunburn. This wavelength range is used to search for highly active star formations.


As the second shortest portion of the electromagnetic spectrum, scientists use energy to measure x-rays. As their name suggests, the frequency of x-rays is so small that they start to look less like waves and more like particles. They produce so much energy that they can severely damage body parts if overexposed. However, their ability to travel through objects makes them ideal for mapping the inside of the human body.

Gamma Rays

With the shortest waves on the spectrum, gamma rays produce so much energy that they can dissolve cell structures. This portion includes every wave beyond 100 keV and can produce gamma explosions more powerful than the sun’s entire lifecycle. Doctors use these particles in controlled environments to target and obliterate cancer cells in patients.

How Are Electromagnetic Waves Observed?

Because of its wide range of frequencies and energies, some aspects of the electromagnetic spectrum have a more difficult time reaching earth than others. For example, gamma rays and x-rays are blocked in the stratosphere, where gases absorb their wavelength. Because of this, astronomers and other researchers must use specific equipment to observe each portion of the spectrum.

Currently, scientists have reliable satellites and observatories collecting data from every wavelength:

  • Greenbank is an earth-based satellite studying radio waves that pass through the atmosphere unobstructed.
  • CARMA measures microwaves from the planet’s surface, while Planck measures their wavelengths that begin to see disruptions.
  • Herschel and Spitzer collect infrared data, which gets absorbed in the stratosphere. In 2021, the James Webb Space Telescope joined these two satellites to observe deep space in low-mid IR.
  • The Hubble Space Telescope, alongside Kepler, observes visible light from orbit. Gemini and Keck join these telescopes from the Earth’s surface.
  • GALEX measures ultraviolet from space alongside Hubble’s updated instruments. Much of the UV frequency dissipates beyond the mesosphere.
  • Chandra, one of NASA’s largest space telescopes, observes X-rays with NuSTAR.
  • Fermi is a telescope that monitors gamma bursts as large as 300 giga-eVs.

The Electromagnetic Spectrum: Further Reading

The electromagnetic spectrum offers many benefits and applications in our everyday lives. From calling on our phones to observing the universe, we can rely on light radiation to help us. Check out the articles below for more on how we use electromagnetic waves.

Frequently Asked Questions

What is the electromagnetic spectrum?

The electromagnetic spectrum is the entire range of light waves that emit from objects. These vary in size depending on their frequency, wavelength, and energy.

What are the 7 electromagnetic spectrums?

The 7 portions of the electromagnetic spectrum are radio waves, microwaves, infrared light, visible light, ultraviolet radiation, x-rays, and gamma rays.

How do we use the electromagnetic spectrum in everyday life?

A wide range of applications exist for every portion of the electromagnetic spectrum. Some practical uses include Geographic Positioning Systems, cell phone communication, x-ray scans, and cancer treatments.

Which color has the highest energy?

Violet has the highest energy of visible light with an average of about 3 electron volts (eV). This compares to red, which has the lowest energy of about 1.5eV.

What color has the longest wavelength?

Red has the longest wavelength of about 700 nanometers (nm). This compares to violet, which has the shortest wavelength of about 400nm.

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