The electromagnetic spectrum, or EM spectrum, is the name given to the collection of all electromagnetic radiation in the universe. It is a type of energy that permeates the cosmos in the form of electric and magnetic waves, allowing the transfer of energy and information.
Discovered over a century ago, the electromagnetic spectrum is the basis on which our universe operates. Without it we could not see, the stars would not shine and life would not exist. It is one of the most important principles that govern everything around us.
It is also an invaluable tool, used by astronomers to probe the depths of the cosmos far beyond what only our eyes can see. The information carried by the electromagnetic spectrum provides almost all of our knowledge about the functioning of everything as we know it.
What is the electromagnetic spectrum?
The EM spectrum is a range of frequencies that corresponds to all the different forms of electromagnetic radiation in the universe. It starts at the highest frequencies, where the waves are stretched the most (low frequency) to very compact waves (high frequency).
These frequencies correspond to different levels of radiation, that is, the transmission of energy through the universe in the form of waves and particles. Low-frequency radiation has much longer wavelengths, which means that the distance between the radiation waves is long, up to several kilometers. At the other end of the spectrum, high frequency radiation has very short wavelengths, trillions of meters long.
The type of radiation emitted by an object depends on its temperature. Things that are cooler emit radiation at lower frequencies and therefore at longer wavelengths. Conversely, things that are warmer emit radiation at higher frequencies and shorter wavelengths.
How is the electromagnetic spectrum organized?
There are seven groups of the electromagnetic spectrum. To the left of the electromagnetic spectrum are radio waves, the lowest frequency form of radiation with the longest wavelengths. Many natural objects emit radio waves, planets to the stars, but also to other phenomena, such as lightning.
Next are microwaves, followed by infrared, visible light (the form of radiation we can see), ultraviolet, x-rays, and gamma rays. All these forms of radiation travel at the same speed in the vacuum of space, the speed of light, or about 300 million meters per second (300,000 km / s).
Each type of EM radiation is created by particles accelerated by an electric field and producing oscillating waves of electric and magnetic fields. The distance between the peaks of these waves is the wavelength of the radiation, while the number of waves is the frequency.
Why is the electromagnetic spectrum important?
The EM spectrum is the means by which our universe transfers energy and information from one place to another. Depending on the type of radiation, however, different knowledge can be gleaned.
Radio waves and microwaves, with their long wavelengths, allow scientists to see in dense molecular clouds where stars are born, which are obscured by other wavelengths. Infrared waves transfer heat, while visible light allows us to see stars and other distant objects.
Ultraviolet light can show us the glow of emerging stars and also reveals the properties of some of the most energetic stars in the universe, such as pulsars. X-rays allow us to probe extremely hot places, such as near black holes Where neutron stars, while gamma rays come from extremely energetic events, such as neutron star collisions.
Who discovered the electromagnetic spectrum?
The discovery of the electromagnetic spectrum is not the result of one person, but rather the work of several scientists over more than a century, who have discovered the different categories of electromagnetic radiation that make up the EM spectrum as we know it. today.
The first discoveries that there were other wavelengths besides visible light came in the 19th century. In 1800, the British astronomer Sir William Herschel used a prism to separate the light and measure the temperature of the resulting colors. He found that beyond red light, where there was no light, the thermometer became hottest – due to invisible infrared light.
In 1867, the Scottish scientist James clerk maxwell predicts the existence of wavelengths in the other direction, beyond the purple end of visible light. The first radio waves, proving that this prediction is correct, were produced by the German physicist Heinrich Hertz in 1887. The last form of radiation to be discovered was x-rays, by the British physicist Ernest Rutherford, in 1914.
Related: How did we find out about the existence of atoms?
Why is the electromagnetic spectrum useful?
Outside of astronomy, we use the EM spectrum for all kinds of things on Earth. First of all, radio waves are very useful for communication, like television and radio, because their long wavelengths allow them to be easily transferred over great distances.
Microwaves are useful for cooking because their frequencies can be easily absorbed by molecules present inside food. Infrared waves are useful for electric heaters because infrared light causes the release of heat through chemical bonds, but also for night vision cameras because infrared cameras can see the glow of infrared light.
Visible light is of course crucial so that we can see everything around us. Ultraviolet radiation, while it can be harmful in large amounts by the sun, can also be used to sterilize water. And gamma rays are useful in medicine, such as targeting and destroying cancer cells.
There are many uses for the electromagnetic spectrum, without which we wouldn’t see much at all in the universe.