The energy of electromagnetic waves

Hello!

This is an advanced topic so if you don't know much math, I would recommend to read it later.

You are most likely reading the article with your eyes, which detect light. Some types of light are different from others, which means that they have different properties despite being the same thing. This may seem simple but stretching the concept allows us to look into a new world of invisible light.

Electromagnetic waves can be found everywhere, from the light we can see to the Wi-Fi we use to the X-rays used in hospitals. All of them have only one difference from each other; their energies of the EM waves are different.

But before that, we have to know that even though in this context EM waves are being called "waves", it can behave as a particle too. This property is known as wave-particle duality. So the energy of EM waves can be the energy in a single photon. It is usually shown by the Planck-Einstein relation:

\(E = hf\)

where \(E\) is the energy of the photon, \(f\) is the frequency of the so-called "wave" and \(h\) is the Planck Constant, which is equal to \(6.62607015 \times 10^{-34} J \times s.\) If you look closely, you will find out that EM waves with a higher frequency have higher energies. The frequency of an EM wave can be shown by this equation:

\(f = \frac{c}{λ}\)

where \(c\) is the speed of the EM wave and \(λ\) is the length of the wavelength. Based on this, if the medium the EM waves pass through is the same for all (which keeps the speed constant), a shorter wavelength means that the EM wave has a higher frequency. The properties of EM waves with different energies allow us to use and find them almost everywhere in our daily lives.

In astronomy, using different wavelength to observe different phenomena will allow us to gain a deeper understanding of the phenomena. For example, certain wavelengths allow us to find the composition of a nebula or galaxy meanwhile other wavelength may help us understand the magnetic fields etc. Radio waves, the EM waves with the lowest energies are being used as a way of sending information to potential aliens!

It is amazing to see that the different wavelengths of just a single thing can bring a lot of variety into how we perceive the universe as we know it.

Thanks for reading!