When speaking about light, the first thought that comes to many will most likely be that which helps our eyes see. However, it is essential to note that this type of light that our eyes are sensitive to is only the beginning – a fraction of the total amount of light that constantly surrounds us. To better describe this long range of light in the universe, scientists have developed the electromagnetic (EM) spectrum. Let us explore this spectrum and some of the well-known types of light associated with it.
The electromagnetic spectrum
Before going into detail about the EM spectrum, it is vital to first know just what exactly it classifies. As mentioned earlier, the light we usually see is one such example. In more scientific terms, this light is a form of electromagnetic waves or electromagnetic radiation. It is a kind of energy that takes on many other forms, such as radio waves and X-rays.
The EM spectrum is a broad range of these electromagnetic waves, most of which are invisible to the naked eye. They are classified from having the lowest energy or the longest wavelength to the highest energy or shortest wavelength. This spectrum is typically divided into seven regions with the following designations in order of their wavelength from longest to shortest:
- Radio waves
- Microwaves
- Infrared (IR)
- Visible light
- Ultraviolet (UV) light
- X-rays
- Gamma rays
Usually, radio waves, which have low levels of energy radiation, are expressed in frequencies. Meanwhile, microwaves, IR, visible light, and UV light are more commonly indicated in wavelengths. Lastly, the last two with the highest radiation energy, x-rays and gamma rays, are measured in electron volts (eV) or the energy of their photons.
What makes these EM waves distinct from one another?
The main factors that distinguish one type of electromagnetic radiation from another are its energy, frequency, and wavelength. Let us first tackle the former. EM radiation can be described in many terms, one of which is photons or streams of mass-less particles. Each of these photons travels in wave-like patterns at the speed of light and contains a particular amount of energy. The varying types of radiation known today are defined by how much energy can be found in their photons. As mentioned above, radio waves contain the lowest energies, followed by microwaves, which have slightly more energy, followed by infrared, and so forth until the most energetic of them all, gamma rays.
Next are frequency and wavelength. A simple electromagnetic wave can be best described as having a shape similar to the letter M, albeit with more curved lines. The peaks are known as crests, while the bottom is called the trough. A wavelength is defined as the distance between crest to crest, usually given in meters, while frequency is defined as the number of waves formed in a given length of time. EM radiation with shorter wavelengths means that its frequency will be higher since a single cycle can pass in a much shorter time.
Applications of the EM spectrum
The EM spectrum finds use in many scientific disciplines, particularly in astronomy. Astronomers utilise the entire spectrum to observe many different things in the cosmos above. For instance, radio and microwaves, which have the lowest energies and longest wavelengths of light, are commonly used to track the movement of cold and dark gasses in space and glean into dense interstellar clouds.
Meanwhile, the wavelengths of IR light are long enough that they can pierce through clouds that would typically block our view. Telescopes that leverage IR light to see are best at finding dim and cool stars, penetrating interstellar dust bands, and even measuring temperatures of cosmic objects like other solar systems.
Conclusion
The EM spectrum is a way to describe all wavelengths of light known to man, both visible and invisible, under normal circumstances. Knowledge of these other types of light and their potential uses allows humankind to leverage them in ways that lead to progress and discoveries both on Earth and beyond space.
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