The Electromagnetic Spectrum

Merriam-Webster’s definition of light is “something that makes vision possible.” However, light is not just limited to white light or the different colors of the rainbow (called visible light). You may be surprised to learn this, but X-rays and other forms of electromagnetic radiation count as light too! There exist forms of light that our eyes cannot see. What we commonly refer to as light is actually only a small part of the whole electromagnetic spectrum.

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Electromagnetic Radiation

The electromagnetic spectrum is the range of all types of electromagnetic radiation. Radiation is the transmission of energy in the form of particles or waves through space or a material medium. Some waves require a medium to travel through, such as air, but electromagnetic waves can move through a vacuum, making it possible for them to travel through space. All electromagnetic radiation travels at the speed of light, which is 186,000 miles per second.

In an electromagnetic wave, the electric and magnetic fields oscillate in directions perpendicular to each other and the direction of the wave. Along with some wave-like properties, electromagnetic radiation also has particle-like properties. These particles are called photons. Therefore, electromagnetic radiation can be thought of as either a stream of photons or a wave.

Matter and Electromagnetic Waves

Matter affects different electromagnetic waves in different ways. Some materials absorb energy from electromagnetic waves. For example, ozone allows infrared light to pass through it with almost no difficulty, but it strongly absorbs energy from ultraviolet light and gamma rays. Sometimes, absorption of electromagnetic radiation can cause chemical reactions to occur. Since vacuums do not contain any matter, they are the only media that are perfectly transparent for electromagnetic radiation to pass through.

Measuring and Describing Waves

Waves are measured in different ways. Frequency is the amount of times a wave passes a given point in a second, measured in Hertz. Wavelength is the distance between corresponding points on a wave, measured in meters. Frequency and wavelength are related--if a wave has a higher frequency, it has a shorter wavelength. If a wave has a lower frequency, it has a longer wavelength. In addition, if a wave has a higher frequency, it has more energy, and vice versa. Energy is measured in electron volts.

Types of Electromagnetic Waves

There are different types of electromagnetic waves. In order of longest to shortest wavelength, there are radio waves, microwaves, infrared waves, visible light, ultraviolet waves, X-rays, and gamma rays.

• Radio waves are the longest waves in the spectrum and have the lowest energy and frequency. One common use is transmitting songs to your radio.

• Microwaves are the next longest waves in the electromagnetic spectrum. They are the type of radiation used in a microwave to heat up your food.

• Infrared waves come next. Night vision goggles work by picking up on infrared light.

• Visible light is the part of the electromagnetic spectrum that humans can see.

• Ultraviolet light is emitted by the sun. One application of UV radiation is in cancer therapy.

• X-rays are used to examine parts of the body, mainly bones and joints.

• Gamma rays have the smallest wavelengths and the highest energy and frequency. They are produced by many hot and energetic objects in the universe, such as neutron stars.

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Although most forms are invisible, electromagnetic radiation has a large impact

in daily life. Your microwave allows you to heat up food in minutes. Too much exposure to the sun’s ultraviolet radiation can give you sunburn. X-rays allow for doctors to assess a patient’s well-being and take steps to provide proper treatment. Next time you turn off your bedside lamp, remember: it may seem dark, but there’s actually a lot more light that you can’t see!

Works Cited

“Electromagnetic Spectrum - Introduction.” NASA, NASA, Mar. 2013,

imagine.gsfc.nasa.gov/science/toolbox/emspectrum1.html.

“The Electromagnetic Spectrum.” HubbleSite.org, 30 May 2019,

hubblesite.org/contents/articles/the-electromagnetic-spectrum.

Electromagnetism, abyss.uoregon.edu/~js/21st_century_science/lectures/lec04.html.