The image shows the diagram of all the electromagnetic radiation existing in the Universe, depending on their wavelengths or frequencies.
All types of electromagnetic radiation make up the electromagnetic spectrum and are of two types, with short wavelength, such as gamma rays, X-rays, then ultraviolet rays, visible light and infrared rays, and long-wavelength radiation, respectively radio waves.
Here, the short wavelength rays are marked on the right side, by a curved line with very frequent loops, representing the short frequency of these gamma and X radiations, with an extremely high energy, which makes them deadly for the human life on Earth.
The three types of harmful radiation, gamma, X and UV, are blocked or absorbed by the Earth’s atmosphere, so that life is possible.
The spectrum continues to the left with short wavelength radiation that can penetrate the Earth’s atmosphere, these being ultraviolet, absorbed by the ozone layer above the atmosphere, light in the visible spectrum that is observable from Earth and infrared radiation absorbed by the atmosphere, which is thermal radiation, released by the Sun and all living bodies through the vibration of molecules and can not be seen with the naked eye, but produce heat easily perceived by the human body.
These radiations are rendered in the central and central-left part of the spectrum, through larger and sparser loops.
At the left end, the loops of the spectrum are widen and scattered greatly, representing radiation with wavelengths longer than IR (infrared) light, classified as microwaves and radio waves, being easily detectable from Earth by certain installations fixed on the ground at high altitudes and used in everyday life.
The electromagnetic spectrum comprises all the electromagnetic radiations from the environment. It is present everywhere in the universe. Even if we can protect ourselves from the artificial radiations, meaning those generated by humans, we cannot protect ourselves entirely from those which occur and are naturally present around us.
There are many types of electromagnetic radiations, of various wavelengths, among which we can name the X-rays, the gamma rays, the ultraviolet light, the visible light, the infrared rays and the radio waves.
The X-rays are used in medicine in order to make radiographies. A radiography is a visual representation, an image, a photo of an internal organ. An example is the lung radiography. X-rays permeate through the human body, and thus, with the help of certain machines, doctors have the possibility to check the health state of the lungs. X-rays are also used in radiotherapy, where their primary role is to destroy the cancer cells.
The ultraviolet light or radiation is a radiation with a wavelength shorter than the light radiation that can be perceived by the naked human eye. A source of ultraviolet radiations is the Sun. The Sun’s light, apart from the visible light, also contains ultraviolet rays. The ultraviolet (abbreviated as UV) radiations are harmful for human health and can lead to skin burns. This is why we have to avoid prolonged exposure under direct sunlight and wear sunscreen during the extremely hot summer days. Maybe you have heard about the UV index during the weather forecast. If this index goes above level 7, it means that sunbathing or staying under direct sunlight for a long time is harmful.
The visible light is a small part of the electromagnetic spectrum which can be perceived by the human eye. There are also lights that the eye cannot see on itself, for example the infrared and the ultraviolet light.
The infrared rays are electromagnetic radiations with wavelengths longer than the visible light. A source of infrared light is the Sun, as well as burning fire and hot or over-heated objects. The infrared light is used in a lot of ways, such as taking photos at night, but also for controlling devices placed at a distance; for example, many remote-controls emit infrared light through which they give commands to the electronic devices.
Radio waves are electromagnetic radiations used for broadcasting radio and TV programs, but are also used for other types of telecommunications. Telecommunications are communications at a distance. Such examples are mobile phones, which use the radio waves in order to communicate with a mobile phone network.
Did you know that radio waves used for radio broadcasting travel faster and better during the nighttime? If you are curious to hear foreign radio stations, turn on your radio, set it on medium waves and try to search for radio stations. During winter nights, if you have a good radio-receiver and a good area for reception, with quiet surroundings, you can be able to hear radio stations even from overseas. This type of listening to broadcasts from very far away is called trans-oceanic DX (which is a telegraphic shortening from “distance” or “distant”).