The electromagnetic spectrum A general term that includes all possible frequencies of electromagnetic radiation.^[1][2][3] The electromagnetic spectrum is also known (usually just called the spectrum) by the ray lines emanating from a black body at a certain temperature (each line has a specific wavelength and frequency). Each chemical element has a spectrum that distinguishes it, that is, it has a set of sequential lines that distinguish it from others, and this spectrum is called an “emission spectrum.” The spectrum of radiation emitted by an object changes with the change in body temperature, and the black color is chosen in particular because it is “ideal” in absorbing rays and is also ideal in emitting radiation. The spectrum of elements is usually in the visible light range.

The electromagnetic spectrum extends from low frequencies such as those used in radio, through medium frequencies such as visible light rays, to high frequencies such as X-rays, and ends with gamma rays. It is considered that the boundary of the shortest wavelength is the Planck length, and the largest possible wavelength is the size of the entire universe. (See Astronomy).^[4]

bands of the electromagnetic spectrum[عدل]

spectrum It is the complete set of electromagnetic waves. In scientific research, we are usually interested in the spectra of elements, as each element is characterized by a distinctive spectrum, such as a fingerprint in people, and it appears in the form of parallel, adjacent light lines of different distinct colors. Spectra of the elements fall mainly in the visible light range of the electromagnetic spectrum – between red light, which has a wavelength of about 700 nanometers, and violet light, which has a wavelength of 400 nanometers (see figure below).

The electromagnetic spectrum consists of waves:

• radio waves
• small waves
• Infrared
• Visible spectrum (red, orange, yellow, green, blue, violet)
• ultraviolet Rays
• X-rays
• gamma rays

These major groups include other minor subgroups.

The electromagnetic spectrum consists of groups of waves that have the same properties but differ in their wavelengths and frequencies. As in the figure:

1- Wireless (radio) groups.

2- Infrared rays.

3- Visible spectrum waves.

4- Ultraviolet rays.

5- X-ray waves.

6- Gamma rays waves.

The table below represents these waves and some of their properties. The electromagnetic spectrum

the group

الطول الموجي (1) 
التردد (هيرتز)
الطاقة (إلكترون فولت)

radio waves

> 910
< 3 × 910
< 510

microwave

610 - 910
3 × 910 - 3 ×1210
-510 - 0.01

Infrared

7000 - 610
3 × 1210 - 4.3 × 1410
0.01 - 2

visible spectrum

4000 - 7000
4.3 ×1410 - 7.5 ×1410
2 - 3

UV

4000 - 10
7.5 × 1410 - 3 × 1710
3 - 310

X ray

10 - 0.1
3 × 1710 - 3 × 1910
310 - 510

gamma rays

< 0.1
> 3 × 1910
> 510

يرتبط تردد الموجة مع طولها الموجي بالعلاقة التالية:

Propagation speed = wavelength x frequency and since its speed is constant, which is the speed of light in vacuum (or air) = 3 x ⁸10 m/s = 300,000,000 m/s.

إذاً: 

Q = l × v d where: Q: the speed of light in a vacuum = 3 × ⁸10 m / s. l: wavelength. td: frequency of the wave.

These waves are used in wireless transmissions such as: 1- Radio transmission 2- Television transmission 3- Radar 4- Aircraft and ship guidance 5- Spacecraft waves

The radio wavelength used for each of these purposes varies. The longest of them are radio waves (long, medium and short waves), and the shortest are radar waves and spacecraft waves, which are called microwaves.

– The ability of radio waves to penetrate ionized layers of air increases as their frequency increases, so short (high-frequency) waves are used in sky waves in order to cover larger areas.

The higher the frequency waves, the more they can penetrate into outer space, such as: television and radar waves, so it is possible to benefit from very short radio waves (microwaves) in communication with satellites and spacecraft because of their ability to penetrate all ionized layers into outer space.

Infrared rays are invisible rays, but we feel their presence through the heat generated by them. They appear in the electromagnetic spectrum at the end of the visible spectrum, and their wavelength ranges from 0.7 to 1 micrometer.

Infrared radiation can study the surfaces of objects and their components. It can also be used to study the types of rocks and minerals that make up the surfaces of objects in imaging.

The body’s radiation of red rays depends on the following: 1- The nature of the body’s surface. 2- Body temperature.

Read also[عدل]

Reference[عدل]

Commons photos and files on: electromagnetic spectrum

• Color Gate
• Electronics portal
• Remote Gateway
• Physics portal
• Optics portal
• Electric gate
• Electromagnetic gate

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