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By the end of this section, you will be able to:
  • Explain how electromagnetic waves are divided into different ranges, depending on wavelength and corresponding frequency
  • Describe how electromagnetic waves in different categories are produced
  • Describe some of the many practical everyday applications of electromagnetic waves

Electromagnetic waves have a vast range of practical everyday applications that includes such diverse uses as communication by cell phone and radio broadcasting, WiFi, cooking, vision, medical imaging, and treating cancer. In this module, we discuss how electromagnetic waves are classified into categories such as radio, infrared, ultraviolet, and so on. We also summarize some of the main applications for each range.

The different categories of electromagnetic waves differ in their wavelength range, or equivalently, in their corresponding frequency ranges. Their properties change smoothly from one frequency range to the next, with different applications in each range. A brief overview of the production and utilization of electromagnetic waves is found in [link] .

Electromagnetic waves
Type of wave Production Applications Issues
Radio Accelerating charges Communications
Remote controls
MRI
Requires control for band use
Microwaves Accelerating charges and thermal agitation Communications
Ovens
Radar
Cell phone use
Infrared Thermal agitation and electronic transitions Thermal imaging
Heating
Absorbed by atmosphere
Greenhouse effect
Visible light Thermal agitation and electronic transitions Photosynthesis
Human vision
Ultraviolet Thermal agitation and electronic transitions Sterilization
Vitamin D production
Ozone depletion
Cancer causing
X-rays Inner electronic transitions and fast collisions Security
Medical diagnosis
Cancer therapy
Cancer causing
Gamma rays Nuclear decay Nuclear medicine
Security
Medical diagnosis
Cancer therapy
Cancer causing
Radiation damage

The relationship c = f λ between frequency f and wavelength λ applies to all waves and ensures that greater frequency means smaller wavelength. [link] shows how the various types of electromagnetic waves are categorized according to their wavelengths and frequencies—that is, it shows the electromagnetic spectrum.

Figure shows the EM spectrum. It shows various types of waves with their wavelengths, frequencies, approximate scales, temperature of bodies emitting those waves and whether those waves penetrate the earth’s atmosphere or not. The waves are: Radio waves, with wavelength of 10 to the power 3 m, frequency of 10 to the power 4 Hz, at the scale of buildings, penetrating the atmosphere; microwaves, with wavelength of 10 to the power minus 2 m, frequency of roughly 10 to the power 10 Hz, at the scale of bees to humans, not penetrating the atmosphere and emitted by bodies at 1 degree K; infrared waves with wavelength of 10 to the power minus 5 m, frequency of roughly 10 to the power 13 Hz, at the scale of a needle point, partly penetrating the atmosphere and emitted by bodies at 100 degree K; visible light waves with wavelength of 0.5 into 10 to the power minus 6 m, frequency of 10 to the power 15 Hz, at the scale of protozoans, penetrating the atmosphere and emitted by bodies at 10,000 degree K; ultraviolet waves with wavelength of 10 to the power minus 8 m, frequency of 10 to the power 16 Hz, at the scale of molecules, not penetrating the atmosphere and emitted by bodies at roughly 5 million degree K; X-rays with wavelength of 10 to the power minus 10 m, frequency of 10 to the power 18 Hz, at the scale of atoms, not penetrating the atmosphere and emitted by bodies above 10 million degree K; Gamma rays with wavelength of 10 to the power minus 12 m, frequency of roughly 10 to the power 20 Hz, at the scale of atomic nuclei, not penetrating the atmosphere and emitted by bodies much above 10 million degree K.
The electromagnetic spectrum, showing the major categories of electromagnetic waves.

Radio waves

The term radio waves    refers to electromagnetic radiation with wavelengths greater than about 0.1 m. Radio waves are commonly used for audio communications (i.e., for radios), but the term is used for electromagnetic waves in this range regardless of their application. Radio waves typically result from an alternating current in the wires of a broadcast antenna. They cover a very broad wavelength range and are divided into many subranges, including microwaves, electromagnetic waves used for AM and FM radio, cellular telephones, and TV signals.

There is no lowest frequency of radio waves, but ELF waves, or “extremely low frequency” are among the lowest frequencies commonly encountered, from 3 Hz to 3 kHz. The accelerating charge in the ac currents of electrical power lines produce electromagnetic waves in this range. ELF waves are able to penetrate sea water, which strongly absorbs electromagnetic waves of higher frequency, and therefore are useful for submarine communications.

Questions & Answers

I'm interested in biological psychology and cognitive psychology
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sammie Reply
physiological Psychology
Nwosu Reply
How can I develope my cognitive domain
Amanyire Reply
why is communication effective
Dakolo Reply
Communication is effective because it allows individuals to share ideas, thoughts, and information with others.
effective communication can lead to improved outcomes in various settings, including personal relationships, business environments, and educational settings. By communicating effectively, individuals can negotiate effectively, solve problems collaboratively, and work towards common goals.
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miss
Every time someone flushes a toilet in the apartment building, the person begins to jumb back automatically after hearing the flush, before the water temperature changes. Identify the types of learning, if it is classical conditioning identify the NS, UCS, CS and CR. If it is operant conditioning, identify the type of consequence positive reinforcement, negative reinforcement or punishment
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Wekolamo
because it helps many people around the world to understand how to interact with other people and understand them well, for example at work (job).
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ARC
A child is a member of community not society elucidate ?
JESSY Reply
Isn't practices worldwide, be it psychology, be it science. isn't much just a false belief of control over something the mind cannot truly comprehend?
Simon Reply
compare and contrast skinner's perspective on personality development on freud
namakula Reply
Skinner skipped the whole unconscious phenomenon and rather emphasized on classical conditioning
war
explain how nature and nurture affect the development and later the productivity of an individual.
Amesalu Reply
nature is an hereditary factor while nurture is an environmental factor which constitute an individual personality. so if an individual's parent has a deviant behavior and was also brought up in an deviant environment, observation of the behavior and the inborn trait we make the individual deviant.
Samuel
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Jonathan
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interpersonal relationships
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Source:  OpenStax, University physics volume 2. OpenStax CNX. Oct 06, 2016 Download for free at http://cnx.org/content/col12074/1.3
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