Electromagnetic Spectrum – Class 12 | Chapter – 8 | Physics Short Notes Series PDF for NEET & JEE
Electromagnetic Spectrum: The electromagnetic spectrum is the range of all electromagnetic waves or radiation, arranged according to their frequency or wavelength. It includes a wide range of waves, from low-frequency radio waves to high-frequency gamma rays, with a corresponding range of energies and wavelengths.
Regions of Electromagnetic Spectrum
The electromagnetic spectrum can be divided into different regions, each with its own characteristic wavelengths, frequencies, and energy ranges. These regions, listed from longest to shortest wavelength, are:
- Radio waves: This region includes the lowest frequencies in the electromagnetic spectrum, from a few hertz to several gigahertz. Radio waves are used for communication, broadcasting, and other applications.
- Microwaves: This region includes higher frequencies than radio waves, ranging from several gigahertz to several hundred gigahertz. Microwaves are used in microwave ovens, communication systems, and other applications.
- Infrared radiation: This region includes electromagnetic waves with frequencies below visible light, ranging from a few hundred gigahertz to several terahertz. Infrared radiation is used in heating, sensing, and imaging applications.
- Visible light: This region includes the frequencies of electromagnetic waves that are visible to the human eye, with wavelengths ranging from about 400 to 700 nanometers. The colors of the rainbow correspond to different frequencies and wavelengths of visible light.
- Ultraviolet radiation: This region includes electromagnetic waves with frequencies above visible light, ranging from several hundred terahertz to several petahertz. Ultraviolet radiation is used in sterilization, fluorescence, and other applications.
- X-rays: This region includes electromagnetic waves with even higher frequencies and energies, ranging from several petahertz to several exahertz. X-rays are used in medical imaging, materials analysis, and other applications.
Gamma rays: This region includes the highest frequencies and energies in the electromagnetic spectrum, with frequencies above several exahertz. Gamma rays are used in medical imaging, radiation therapy, and other applications.
Electromagnetic Waves in Electromagnetic Spectrum
The entire range (electromagnetic spectrum) is given by radio waves, microwaves, infrared radiation, visible light, ultra-violet radiation, X-rays, gamma rays and cosmic rays in the increasing order of frequency and decreasing order of wavelength. The type of radiation and their frequency and wavelength ranges are as follows:
|Type of Radiation||Frequency Range (Hz)||Wavelength Range|
|gamma-rays||1020 – 1024||< 10-12 m|
|x-rays||1017 – 1020||1 nm – 1 pm|
|ultraviolet||1015 – 1017||400 nm – 1 nm|
|visible||4 x 1014 – 7.5 x 1014||750 nm – 400 nm|
|near-infrared||1 x 1014 – 4 x1014||2.5 μm – 750 nm|
|infrared||1013 – 1014||25 μm – 2.5 μm|
|microwaves||3 x 1011 – 1013||1 mm – 25 μm|
|radio waves||< 3 x 1011||> 1 mm|
Significance of Electromagnetic Spectrum
The electromagnetic spectrum is significant in many areas of science and technology, including physics, chemistry, astronomy, and engineering. Here are some of the key aspects of its significance:
- Understanding the properties of electromagnetic waves: The electromagnetic spectrum provides a comprehensive framework for understanding the properties of electromagnetic waves, including their wavelengths, frequencies, and energies. This knowledge is fundamental to many areas of science and technology, including optics, materials science, and electronics.
- Communication and broadcasting: The different regions of the electromagnetic spectrum are used for various forms of communication and broadcasting, including radio and TV broadcasting, satellite communication, cellular networks, and Wi-Fi. This has revolutionized the way people communicate and connect with one another across the globe.
- Medical imaging and treatment: X-rays, gamma rays, and other forms of electromagnetic radiation are used in medical imaging and treatment, such as X-ray and CT scans, radiation therapy, and nuclear medicine. These technologies have greatly improved the ability of doctors to diagnose and treat diseases.
- Remote sensing: The electromagnetic spectrum is used in remote sensing technologies to study the Earth’s atmosphere, oceans, and surface features. These technologies include weather satellites, remote sensing satellites, and airborne sensors.
- Astronomy: The electromagnetic spectrum is used in astronomy to study the universe, including the detection of distant stars, galaxies, and other celestial objects. Astronomers use a wide range of telescopes and instruments that detect different regions of the electromagnetic spectrum, including visible light, radio waves, and X-rays.
Materials science and engineering: The electromagnetic spectrum is used in materials science and engineering to study the properties of materials and develop new materials for various applications. Techniques such as X-ray diffraction, infrared spectroscopy, and Raman spectroscopy use different regions of the electromagnetic spectrum to probe the structure and properties of materials.
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