The Electromagnetic Spectrum

The EM spectrum is an important concept in physics. It is how the universe transfers energy and information from one location to another. It has many applications in our lives, from the radio to the microwave. In this article, we'll discuss it even further!!

The Basics: What Even IS This "Spectrum"?

The electromagnetic (EM) spectrum encompasses all types of electromagnetic radiation, organized by frequency or wavelength. It includes a wide range of waves, from long radio waves to very short gamma rays.

The characteristics of the waves

• Speed: These waves all travel at the speed of light (approximately 300,000 km/h), regardless of their wavelength and frequency… But why do they all have the same speed?

  That is because they are all self-propagating oscillations of electric and magnetic fields. The speed of light (c) is a fundamental constant of the universe, determined by the properties of space itself.

• Frequency: It is the number of waves passing in a certain time. It uses the unit Hertz (Hz).

• Wavelength: It is the distance between two consecutive crests or two consecutive troughs on a single wave. Also, there is an inverse relationship between the frequency and wavelength of a wave. This means that as the frequency of a wave increases, its wavelength decreases, and vice versa.

Now, let’s meet the family!

(Image credit: Getty Images)

Journey through the spectrum (according to wavelength) 

• Radio waves

It has the longest wavelength and the lowest frequency in the electromagnetic spectrum. It's usually used for communications like radio, TV, and cell phones. It's generated by accelerating charged particles, such as electric currents. Unlike light, radio waves can easily pass through buildings and obstacles, which is why your phone can still get signal indoors!

• Microwaves

It has a shorter wavelength and higher frequency than radio waves, putting it between radio waves and infrared on the EM spectrum. It's best known for heating food in microwave ovens by making water molecules vibrate, but it's also used in radar (like for weather or speed guns). Microwaves are easily absorbed by water, which is why your food gets hot (and sometimes only the plate).

• Infrared

It has a wavelength longer than visible light but shorter than microwaves, and its main characteristic is that we feel it as heat. Everything warm, including people and animals, emits infrared. It's used in TV remotes, night vision goggles, thermal cameras, and even to keep food warm. Think of it as the "heat vision" of the EM spectrum.

• Visible Light

It's the only part of the electromagnetic spectrum that our eyes can see. It has wavelengths between infrared and ultraviolet, appearing to us as a spectrum of colors from red (longest wavelength) to violet (shortest wavelength). 

• Ultraviolet

It has a shorter wavelength and higher frequency than visible light, making it invisible.  Characterized by its ability to cause chemical reactions and ionization, UV radiation is utilized in sterilization, water purification, and forensic analysis.

While necessary for Vitamin D synthesis, excessive UV exposure, primarily from the sun, can cause DNA damage.

• X-rays 

X-rays, sometimes referred to as Röntgen radiation after their discoverer, Wilhelm Röntgen, are a form of high-energy electromagnetic radiation. They were named "X-rays" to indicate that they were an unknown type of radiation at the time of their discovery. X-rays are widely used in medical diagnostics and materials science, such as in the identification of chemical elements.

• Gamma Rays

They represent the highest energy and shortest wavelength region of the electromagnetic spectrum, originating from atomic nuclei. Produced by nuclear processes such as radioactive decay, fusion, and cosmic phenomena (e.g., supernovae and active galactic nuclei).

After all, studying the EM spectrum is crucial in understanding many physics concepts and applications like waves, atomic theories, and even nuclear physics. 

Reference List

BBC Bitesize. (n.d.). EM waves and the electromagnetic spectrum - Electromagnetic waves - Edexcel - GCSE Physics (Single Science) Revision - Edexcel. [online] Available at: https://www.bbc.co.uk/bitesize/guides/z32f4qt/revision/1.

O’Callaghan, J. (2021). What is the electromagnetic spectrum? [online] Space.com. Available at: https://www.space.com/what-is-the-electromagnetic-spectrum.

Wikipedia Contributors (2019). Radio wave. [online] Wikipedia. Available at: https://en.wikipedia.org/wiki/Radio_wave.

Wikipedia Contributors (2019). Microwave. [online] Wikipedia. Available at: https://en.wikipedia.org/wiki/Microwave.

NASA (2023). Infrared Waves | Science Mission Directorate. [online] science.nasa.gov. Available at: https://science.nasa.gov/ems/07_infraredwaves/.

BYJUS (2017). Visible Light. [online] BYJUS. Available at: https://byjus.com/physics/visible-light/.

Wikipedia Contributors (2019). Ultraviolet. [online] Wikipedia. Available at: https://en.wikipedia.org/wiki/Ultraviolet.

‌Wikipedia Contributors (2019). X-ray. [online] Wikipedia. Available at: https://en.wikipedia.org/wiki/X-ray.

Wikipedia Contributors (2019). Gamma ray. [online] Wikipedia. Available at: https://en.wikipedia.org/wiki/Gamma_ray.