Electromagnetic radiation | Spectrum, Examples, & Types

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border-right-sm border-left-sm open"> <div class="drawer d-flex flex-column open"> <div class="left-rail-section-content"> <div class="topic-left-rail-header text-truncate bg-gray-50 position-relative text-right d-flex align-items-center"> <div class="tlr-title px-20 py-15 text-left"> <em class="material-icons text-gray-400 d-lg-none" data-icon="toc"></em> <a class="font-serif font-weight-bold text-black link-blue" href="https://www.britannica.com/science/electromagnetic-radiation">electromagnetic radiation</a> </div> <button aria-label="Close" class="js-sections-close-button btn-link btn-sm btn d-lg-none position-absolute top-0 p-10 right-0" > <em class="material-icons font-26" data-icon="close"></em> </button> </div> <div class="section-content pl-10 pr-20 pl-sm-50 pr-sm-60 pl-lg-5 pr-lg-10 pt-10 pt-lg-0 bg-gray-50 clear-catfish-ad"> <div class="toc mb-20"> <div class="font-serif font-14 font-weight-bold mx-15 mb-15 mt-20"> Table of Contents </div> <ul class="list-unstyled my-0" data-level="h1"><li data-target="#ref1"><div class="pl-25"><a class="link-gray-900 w-100" href="/science/electromagnetic-radiation">Introduction</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref59188"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation#ref59188">General considerations</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref59189"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation#ref59189">Occurrence and importance</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref59190"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/The-electromagnetic-spectrum">The electromagnetic spectrum</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref59191"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/The-electromagnetic-spectrum#ref59191">Generation of electromagnetic radiation</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref59913"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Continuous-spectra-of-electromagnetic-radiation">Continuous spectra of electromagnetic radiation</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref59914"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Continuous-spectra-of-electromagnetic-radiation#ref59914">Discrete-frequency sources and absorbers of electromagnetic radiation</a></li></ul></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref59192"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Properties-and-behaviour">Properties and behaviour</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref59915"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Properties-and-behaviour#ref59915">Scattering, reflection, and refraction</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref59916"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Properties-and-behaviour#ref59916">Superposition and interference</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref59917"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Properties-and-behaviour#ref59917">Propagation and coherence</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref59918"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Properties-and-behaviour#ref59918">Speed of electromagnetic radiation and the Doppler effect</a></li></ul></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref59193"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Properties-and-behaviour#ref59193">Cosmic background electromagnetic radiation</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref59194"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Effect-of-gravitation">Effect of gravitation</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref59195"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Effect-of-gravitation#ref59195">The greenhouse effect of the atmosphere</a></li></ul></div></li><li data-target="#ref59180"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Effect-of-gravitation#ref59180">Forms of electromagnetic radiation</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref59181"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Radio-waves">Radio waves</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref59182"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Microwaves">Microwaves</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref59183"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Microwaves#ref59183">Infrared radiation</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref59184"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Microwaves#ref59184">Visible radiation</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref59185"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Ultraviolet-radiation">Ultraviolet radiation</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref59186"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Ultraviolet-radiation#ref59186">X-rays</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref59187"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Gamma-rays">Gamma rays</a></li></ul></div></li><li data-target="#ref11353"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Gamma-rays#ref11353">Historical survey</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref11354"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Gamma-rays#ref11354">Development of the classical radiation theory</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref11355"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Gamma-rays#ref11355">Wave theory and corpuscular theory</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref11356"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Relation-between-electricity-and-magnetism">Relation between electricity and magnetism</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref11357"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Relation-between-electricity-and-magnetism#ref11357">The electromagnetic wave and field concept</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref11358"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Relation-between-electricity-and-magnetism#ref11358">Speed of light</a></li></ul></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref11359"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Development-of-the-quantum-theory-of-radiation">Development of the quantum theory of radiation</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref11360"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Development-of-the-quantum-theory-of-radiation#ref11360">Radiation laws and Planck’s light quanta</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref11361"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Development-of-the-quantum-theory-of-radiation#ref11361">Photoelectric effect</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref11362"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Compton-effect">Compton effect</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref11363"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Compton-effect#ref11363">Resonance absorption and recoil</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref11364"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Compton-effect#ref11364">Wave-particle duality</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref11365"><a class="w-100 link-gray-900" href="/science/electromagnetic-radiation/Quantum-electrodynamics">Quantum electrodynamics</a></li></ul></li></ul></div></li></ul> <a class="toc-extra-link link-gray-900" href="https://www.britannica.com/science/electromagnetic-radiation/additional-info">References & Edit History</a> <a class="toc-extra-link link-gray-900" href="/facts/electromagnetic-radiation">Quick Facts & Related Topics</a> 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Let us know if you have suggestions to improve this article (requires login). </div> <div class="type-menu"> <label for="feedback-type" class="label mb-10">Feedback Type</label> <select id="feedback-type" class="form-select mb-30" name="feedbackTypeId" required> <option value="" selected="selected">Select a type (Required)</option> <option value="1">Factual Correction</option> <option value="2">Spelling/Grammar Correction</option> <option value="3">Link Correction</option> <option value="4">Additional Information</option> <option value="5">Other</option> </select> </div> <label for="feedback" class="label mb-10">Your Feedback</label> <textarea id="feedback" class="form-control mb-30" name="feedback" maxlength="3000" rows="7" required></textarea> <button class="btn btn-blue" type="submit">Submit Feedback</button> </form> <div class="success-messaging d-none mt-30"> <div class="title">Thank you for your feedback</div> <p>Our editors will review what you’ve submitted and determine whether to revise the article.</p> </div> </div> </div> <div class="md-websites-modal size-lg d-none"> <div class="md-modal-body"> <div class="h2 font-serif pb-15 border-bottom font-weight-bold"> External Websites </div> <div class="pb-20"> <ul class="list-unstyled mt-20 lh-lg"> <li><a class="external" href="https://www.khanacademy.org/science/ap-physics-2/ap-light-waves/ap-introduction-to-light-waves/v/electromagnetic-waves-and-the-electromagnetic-spectrum" target="_blank" rel="noopener ">Khan Academy - Electromagnetic waves and the electromagnetic spectrum</a></li> <li><a class="external" href="https://www.frontiersin.org/journals/public-health/articles/10.3389/fpubh.2021.691880/full" target="_blank" rel="noopener ">Frontiers - Frontiers in Public Health - Effects of Radiofrequency Electromagnetic Radiation on Neurotransmitters in the Brain</a></li> <li><a class="external" href="https://pressbooks.online.ucf.edu/osuniversityphysics2/chapter/maxwells-equations-and-electromagnetic-waves/" target="_blank" rel="noopener ">University of Central Florida Pressbooks - Maxwell’s Equations and Electromagnetic Waves</a></li> <li><a class="external" href="https://uomustansiriyah.edu.iq/media/lectures/6/6_2018_05_02!06_05_40_PM.pdf" target="_blank" rel="noopener ">Mustansiriyah University - The nature of electromagnetic radiation.</a></li> <li><a class="external" href="https://ehs.lbl.gov/resource/documents/radiation-protection/non-ionizing-radiation/electromagnetic-radiation-and-fields/" target="_blank" rel="noopener ">Lawrence Berkeley National Laboratory - Environment, Health and Safety - Electromagnetic Radiation and Fields</a></li> <li><a class="external" href="https://micro.magnet.fsu.edu/primer/lightandcolor/electromaghome.html" target="_blank" rel="noopener ">Molecular Expressions - Electromagnetic Radiation</a></li> <li><a class="external" href="https://www.academia.edu/41754542/BASICS_OF_ELECTROMAGNETIC_RADIATION" target="_blank" rel="noopener ">Academia - Basics of electromagnetic radiation</a></li> <li><a class="external" href="https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Spectroscopy/Fundamentals_of_Spectroscopy/Electromagnetic_Radiation" target="_blank" rel="noopener ">Chemistry LibreTexts - Electromagnetic Radiation</a></li> <li><a class="external" href="https://scholar.harvard.edu/files/david-morin/files/waves_electromagnetic.pdf" target="_blank" rel="noopener ">Scholars at HARVARD - Electromagnetic waves</a></li> <li><a class="external" href="https://www.e-education.psu.edu/geog160/node/1958" target="_blank" rel="noopener ">Pennsylvania State University - Mapping our Changing World - Electromagnetic Radiation</a></li> <li><a class="external" href="https://digitalcommons.uri.edu/cgi/viewcontent.cgi?article=1035&context=phy204-lecturenotes" target="_blank" rel="noopener ">DigitalCommons at URI - Electromagnetic waves. Poynting vector. Another glimpse of relativityrelativity (PDF)</a></li> </ul> </div> </div> </div> </div> </div> <div class="toc-header-marker"></div> <button class="ai-ask-button btn btn-sm border-2 btn-outline-red-400 border-red-400 d-none mr-0 mr-lg-10 ml-5 ml-sm-10 ml-lg-0 p-10 px-sm-5 px-md-10 js-header-ai-ask-button"> Ask the Chatbot a Question </button> <div class="caption alternate-titles">Also known as: electromagnetic wave</div> <div class="md-byline module-spacing "> <div class="font-serif font-12"> <span class="written-by text-gray-700"> Written by </span> <div class="editor-popover popover p-0"> <a class="d-block p-20 qa-editor-popup gtm-byline font-12 byline-contributor" href="/contributor/Melba-Phillips/2307" > <div class="editor-title font-16 font-weight-bold">Melba Phillips</div> <div class="editor-description font-12 font-serif mt-5 clamp-description text-black">Emerita Professor of Physics, University of Chicago. Coauthor of <i>Classical Electricity and Magnetism.</i></div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link gtm-byline font-12 byline-contributor text-decoration-underline"> Melba Phillips</span>, <div class="editor-popover popover p-0"> <a class="d-block p-20 qa-editor-popup gtm-byline font-12 byline-contributor" href="/contributor/Hellmut-Fritzsche/3535" > <div class="editor-title font-16 font-weight-bold">Hellmut Fritzsche</div> <div class="editor-description font-12 font-serif mt-5 clamp-description text-black">Louis Block Professor of Physics, University of Chicago.</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link gtm-byline font-12 byline-contributor text-decoration-underline"> Hellmut Fritzsche</span><span class="text-gray-700 mx-5">•</span><a class="see-all border-gray-700 gtm-byline" rel="nofollow" href="https://www.britannica.com/science/electromagnetic-radiation/additional-info#contributors">All</a> </div> <div class="font-serif font-12 text-gray-700"> <span class="qa-fact-checked-by">Fact-checked by</span> <div class="editor-popover popover p-0"> <a class="d-block p-20 qa-editor-popup font-12" href="/editor/The-Editors-of-Encyclopaedia-Britannica/4419" > <div class="editor-title font-16 font-weight-bold">The Editors of Encyclopaedia Britannica</div> <div class="editor-description font-12 font-serif mt-5 text-black">Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. They write new content and verify and edit content received from contributors.</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link font-12 "> The Editors of Encyclopaedia Britannica</span></div> <div class="last-updated font-12 font-serif"> <span class="text-gray-700"> Last Updated: <time datetime="2025-02-12T00:00:00CST" >Feb 12, 2025</time> •</span> <a class="byline-edit-history" href="https://www.britannica.com/science/electromagnetic-radiation/additional-info#history" rel="nofollow">Article History</a> </div></div> </div> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button d-none d-sm-block js-sections-inline-button module-spacing btn d-lg-none"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <div class="d-flex d-sm-none flex-row"> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button js-sections-inline-button module-spacing"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <button class="ai-ask-button btn btn-sm border-2 btn-outline-red-400 border-red-400 module-spacing js-inline-ai-ask-button p-10 ml-5"> Ask the Chatbot </button> </div> <div class="js-qf-module qf-module px-40 px-sm-20 py-15 mx-auto module-spacing font-14 bg-gray-50 rounded"> <div class="facts-list mt-10"> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Key People: </dt> <dd><a href="/biography/James-Clerk-Maxwell" topicid="370621">James Clerk Maxwell</a></dd> <dd><a href="/biography/Christiaan-Huygens" topicid="277775">Christiaan Huygens</a></dd> <dd><a href="/biography/Thomas-Young" topicid="653983">Thomas Young</a></dd> <dd><a href="/biography/Hendrik-Antoon-Lorentz" topicid="348120">Hendrik Antoon Lorentz</a></dd> <dd><a href="/biography/Francois-Arago" topicid="31875">François Arago</a></dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> </div> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Related Topics: </dt> <dd><a href="/science/light" topicid="340440">light</a></dd> <dd><a href="/science/luminescence" topicid="351229">luminescence</a></dd> <dd><a href="/science/X-ray" topicid="650351">X-ray</a></dd> <dd><a href="/science/photoelectric-effect" topicid="457841">photoelectric effect</a></dd> <dd><a href="/science/gamma-ray" topicid="225048">gamma ray</a></dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> <div class="text-center"> <a class="btn btn-sm btn-link p-0" href="/facts/electromagnetic-radiation"> See all related content </a> </div> </div> </div> </div><span class="marker before-article"></span><section data-level="1" id="ref1"><span class="marker PREMOD1 mod-inline"></span><p class="topic-paragraph"><strong><span id="ref321601"></span>electromagnetic radiation</strong>, in classical <a href="https://www.britannica.com/science/physics-science" class="md-crosslink autoxref " data-show-preview="true">physics</a>, the flow of <a href="https://www.britannica.com/science/energy" class="md-crosslink " data-show-preview="true">energy</a> at the universal <a href="https://www.britannica.com/science/speed-of-light" class="md-crosslink " data-show-preview="true">speed of light</a> through free space or through a material medium in the form of the <a href="https://www.britannica.com/science/electric-field" class="md-crosslink " data-show-preview="true">electric</a> and <a href="https://www.britannica.com/science/magnetic-field" class="md-crosslink " data-show-preview="true">magnetic fields</a> that make up electromagnetic waves such as <a href="https://www.britannica.com/science/radio-wave" class="md-crosslink " data-show-preview="true">radio waves</a>, <a href="https://www.britannica.com/science/light" class="md-crosslink " data-show-preview="true">visible light</a>, and <a href="https://www.britannica.com/science/gamma-ray" class="md-crosslink " data-show-preview="true">gamma rays</a>. In such a <a href="https://www.britannica.com/science/wave-water" class="md-crosslink autoxref " data-show-preview="true">wave</a>, time-varying electric and magnetic fields are mutually linked with each other at right angles and perpendicular to the direction of motion. An electromagnetic wave is <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="characterized" href="https://www.britannica.com/dictionary/characterized" data-type="EB">characterized</a> by its intensity and the <a href="https://www.britannica.com/science/frequency-physics" class="md-crosslink autoxref " data-show-preview="true">frequency</a> ν of the time variation of the electric and magnetic fields.</p><span class="marker MOD1 mod-inline"></span><span class="marker PREMOD2 mod-inline"></span><p class="topic-paragraph">In terms of the modern <a href="https://www.britannica.com/science/quantum-mechanics-physics" class="md-crosslink " data-show-preview="true">quantum theory</a>, electromagnetic radiation is the flow of <a href="https://www.britannica.com/science/photon" class="md-crosslink " data-show-preview="true">photons</a> (also called light quanta) through space. Photons are packets of energy <em>h</em>ν that always move with the universal speed of light. The symbol <em>h</em> is <a href="https://www.britannica.com/science/Plancks-constant" class="md-crosslink " data-show-preview="true">Planck’s constant</a>, while the value of ν is the same as that of the frequency of the electromagnetic wave of classical theory. Photons having the same energy <em>h</em>ν are all alike, and their number <a href="https://www.britannica.com/science/density" class="md-crosslink autoxref " data-show-preview="true">density</a> corresponds to the intensity of the <a href="https://www.britannica.com/science/radiation" class="md-crosslink autoxref " data-show-preview="true">radiation</a>. Electromagnetic radiation exhibits a multitude of phenomena as it interacts with charged particles in <a href="https://www.britannica.com/science/atom" class="md-crosslink " data-show-preview="true">atoms</a>, <a href="https://www.britannica.com/science/molecule" class="md-crosslink " data-show-preview="true">molecules</a>, and larger objects of matter. These phenomena as well as the ways in which electromagnetic radiation is created and observed, the manner in which such radiation occurs in nature, and its technological uses depend on its frequency ν. The <a href="https://www.britannica.com/science/spectrum" class="md-crosslink autoxref " data-show-preview="true">spectrum</a> of frequencies of electromagnetic radiation extends from very low <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="values" href="https://www.britannica.com/dictionary/values" data-type="EB">values</a> over the range of radio waves, <a href="https://www.britannica.com/technology/television-technology" class="md-crosslink " data-show-preview="true">television</a> waves, and <a href="https://www.britannica.com/science/microwave-radiation" class="md-crosslink " data-show-preview="true">microwaves</a> to visible light and beyond to the substantially higher values of <a href="https://www.britannica.com/science/ultraviolet-radiation" class="md-crosslink " data-show-preview="true">ultraviolet light</a>, <a href="https://www.britannica.com/science/X-ray" class="md-crosslink " data-show-preview="true">X-rays</a>, and gamma rays.</p><span class="marker MOD2 mod-inline"></span><span class="marker PREMOD3 mod-inline"></span><p class="topic-paragraph">The basic properties and behaviour of electromagnetic radiation are discussed in this article, as are its various forms, including their sources, distinguishing characteristics, and practical applications. The article also traces the development of both the classical and <a href="https://www.britannica.com/science/quantum" class="md-crosslink autoxref " data-show-preview="true">quantum</a> theories of radiation.</p><span class="marker MOD3 mod-inline"></span></section> <span class="marker h2"></span><section data-level="1" id="ref59188"> <h2 class="h1">General considerations</h2> <section data-level="2" id="ref59189"> <h2 class="h2">Occurrence and importance</h2> <span class="marker PREMOD4 mod-inline"></span><p class="topic-paragraph">Close to 0.01 percent of the mass/energy of the entire <a href="https://www.britannica.com/science/universe" class="md-crosslink " data-show-preview="true">universe</a> occurs in the form of electromagnetic radiation. All human <span id="ref273238"></span><a href="https://www.britannica.com/science/life" class="md-crosslink " data-show-preview="true">life</a> is immersed in it, and modern communications technology and medical services are particularly dependent on one or another of its forms. In fact, all living things on Earth depend on the electromagnetic radiation received from the <span id="ref273239"></span><a href="https://www.britannica.com/place/Sun" class="md-crosslink " data-show-preview="true">Sun</a> and on the transformation of <a href="https://www.britannica.com/science/solar-energy" class="md-crosslink autoxref " data-show-preview="true">solar energy</a> by <a href="https://www.britannica.com/science/photosynthesis" class="md-crosslink " data-show-preview="true">photosynthesis</a> into <a href="https://www.britannica.com/plant/plant" class="md-crosslink " data-show-preview="true">plant</a> life or by biosynthesis into <a href="https://www.britannica.com/science/zooplankton" class="md-crosslink " data-show-preview="true">zooplankton</a>, the basic step in the <a href="https://www.britannica.com/science/food-chain" class="md-crosslink " data-show-preview="true">food chain</a> in <a href="https://www.britannica.com/science/ocean" class="md-crosslink " data-show-preview="true">oceans</a>. The <a href="https://www.britannica.com/science/human-eye" class="md-crosslink " data-show-preview="true">eyes</a> of many animals, including those of humans, are adapted to be sensitive to and hence to see the most abundant part of the Sun’s electromagnetic radiation—namely, <a href="https://www.britannica.com/science/light" class="md-crosslink " data-show-preview="true">light</a>, which <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="comprises" href="https://www.merriam-webster.com/dictionary/comprises" data-type="MW">comprises</a> the visible portion of its wide range of frequencies. Green plants also have high sensitivity to the maximum intensity of solar electromagnetic radiation, which is absorbed by a substance called <a href="https://www.britannica.com/science/chlorophyll" class="md-crosslink " data-show-preview="true">chlorophyll</a> that is essential for plant growth via photosynthesis.</p><span class="marker MOD4 mod-inline"></span> <span class="marker PREMOD5 mod-inline"></span><p class="topic-paragraph">Practically all the fuels that modern society uses—<a href="https://www.britannica.com/science/natural-gas" class="md-crosslink " data-show-preview="true">gas</a>, <a href="https://www.britannica.com/science/petroleum" class="md-crosslink " data-show-preview="true">oil</a>, and <a href="https://www.britannica.com/science/coal-fossil-fuel" class="md-crosslink " data-show-preview="true">coal</a>—are stored forms of energy received from the Sun as electromagnetic radiation millions of years ago. Only the energy from <a href="https://www.britannica.com/technology/nuclear-reactor" class="md-crosslink " data-show-preview="true">nuclear reactors</a> does not originate from the Sun.</p><a class="link-module shadow-sm d-block qa-quiz-module" href="/quiz/matter-and-more-quiz" data-link-module-iframe-link=""> <img loading="lazy" src="https://cdn.britannica.com/05/215905-131-626D860A/Encyclopaedia-Britannica-thistle-graphic-logo.jpg" alt="Encyclopaedia Britannica thistle graphic to be used with a Mendel/Consumer quiz in place of a photograph." class="rounded-sm mr-15" width="70" /> <div class="line-clamp clamp-5"> <div class="module-title bg-green">Britannica Quiz</div> <div class="font-weight-semi-bold mt-5">Matter and More Quiz</div> </div> </a><div class="one-good-fact-module"> </div><span class="marker MOD5 mod-inline"></span> <span class="marker PREMOD6 mod-inline"></span><p class="topic-paragraph">Everyday life is pervaded by artificially made electromagnetic radiation: food is heated in <a href="https://www.britannica.com/technology/microwave-oven" class="md-crosslink " data-show-preview="true">microwave ovens</a>, <a href="https://www.britannica.com/technology/airplane" class="md-crosslink " data-show-preview="true">airplanes</a> are guided by <a href="https://www.britannica.com/technology/radar" class="md-crosslink " data-show-preview="true">radar</a> waves, <a href="https://www.britannica.com/technology/television-technology" class="md-crosslink " data-show-preview="true">television</a> sets receive electromagnetic waves <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="transmitted" href="https://www.britannica.com/dictionary/transmitted" data-type="EB">transmitted</a> by broadcasting stations, and <a href="https://www.britannica.com/science/infrared-radiation" class="md-crosslink " data-show-preview="true">infrared</a> waves from heaters provide warmth. Infrared waves also are given off and received by automatic self-focusing <a href="https://www.britannica.com/technology/camera" class="md-crosslink " data-show-preview="true">cameras</a> that electronically measure and set the correct distance to the object to be photographed. As soon as the Sun sets, <a href="https://www.britannica.com/technology/incandescent-lamp" class="md-crosslink " data-show-preview="true">incandescent</a> or <a href="https://www.britannica.com/technology/fluorescent-lamp" class="md-crosslink " data-show-preview="true">fluorescent lights</a> are turned on to provide artificial illumination, and cities glow brightly with the colourful fluorescent and <a href="https://www.britannica.com/science/neon-chemical-element" class="md-crosslink " data-show-preview="true">neon</a> lamps of advertisement signs. Familiar too is <a href="https://www.britannica.com/science/ultraviolet-radiation" class="md-crosslink " data-show-preview="true">ultraviolet radiation</a>, which the eyes cannot see but whose effect is felt as pain from <a href="https://www.britannica.com/science/sunburn" class="md-crosslink " data-show-preview="true">sunburn</a>. Ultraviolet light represents a kind of electromagnetic radiation that can be harmful to <a href="https://www.britannica.com/science/life" class="md-crosslink " data-show-preview="true">life</a>. Such is also true of <a href="https://www.britannica.com/science/X-ray" class="md-crosslink " data-show-preview="true">X-rays</a>, which are important in <a href="https://www.britannica.com/science/medicine" class="md-crosslink " data-show-preview="true">medicine</a> as they allow physicians to observe the inner parts of the body but exposure to which should be kept to a minimum. Less familiar are <a href="https://www.britannica.com/science/gamma-ray" class="md-crosslink " data-show-preview="true">gamma rays</a>, which come from <a href="https://www.britannica.com/science/nuclear-reaction" class="md-crosslink " data-show-preview="true">nuclear reactions</a> and <a href="https://www.britannica.com/science/radioactivity" class="md-crosslink " data-show-preview="true">radioactive</a> <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="decay" href="https://www.britannica.com/dictionary/decay" data-type="EB">decay</a> and are part of the harmful high-energy radiation of radioactive materials and <a href="https://www.britannica.com/technology/nuclear-weapon" class="md-crosslink " data-show-preview="true">nuclear weapons</a>.</p><span class="marker MOD6 mod-inline"></span> </section> </section><span class="marker end-of-content"></span><span class="marker after-article"></span></div> <div id="chatbot-simplify-root"></div> <div id="chatbot-root"></div> </div> </div> </div> <div class="ai-dialog-placeholder"></div> </div> </div> <aside class="col-md-da-320"></aside> </div> </div> </div> </div> </article> </div> </div> </div> </div> </main> <div id="md-footer"></div> <noscript><iframe src="//www.googletagmanager.com/ns.html?id=GTM-5W6NC8" height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript>  <script> window.ap3c = window.ap3c || {}; var ap3c = window.ap3c; ap3c.cmd = ap3c.cmd || []; ap3c.cmd.push(function() { ap3c.init('ZO4siT4cLwnykPnzZWJtd3Byb2Q', 'https://engage.email.britannica.com/'); ap3c.track({v: 0}); }); ap3c.activity = function(act) { ap3c.act = (ap3c.act || []); ap3c.act.push(act); }; var s, t; s = document.createElement('script'); s.type = 'text/javascript'; s.src = "https://engage.email.britannica.com/app.js"; t = document.getElementsByTagName('script')[0]; t.parentNode.insertBefore(s, t); </script> <script class="marketing-page-info" type="application/json"> {"pageType":"Topic","templateName":"DESKTOP","pageNumber":1,"pagesTotal":13,"pageId":183228,"pageLength":735,"initialLoad":true,"lastPageOfScroll":false} </script> <script class="marketing-content-info" type="application/json"> [] </script> <script src="https://cdn.britannica.com/mendel-resources/3-133/js/libs/jquery-3.5.0.min.js?v=3.133.36"></script> <script type="text/javascript" data-type="Init Mendel Code Splitting"> (function() { $.ajax({ dataType: 'script', cache: true, url: 'https://cdn.britannica.com/mendel-resources/3-133/dist/topic-page.js?v=3.133.36' }); })(); </script> <script class="analytics-metadata" type="application/json"> {"leg":"D","adLeg":"D","userType":"ANONYMOUS","pageType":"Topic","pageSubtype":null,"articleTemplateType":"PAGINATED","gisted":false,"pageNumber":1,"hasSummarizeButton":false,"hasAskButton":true} </script> <script type="text/javascript"> EBStat={accountId:-1,hostnameOverride:'webstats.eb.com',domain:'www.britannica.com', json:''}; </script> <script type="text/javascript"> ( function() { $.ajax( { dataType: 'script', cache: true, url: '//www.britannica.com/webstats/mendelstats.js?v=1' } ) .done( function() { try {writeStat(null,EBStat);} catch(err){} } ); })(); </script> <div id="bc-fixed-dialogue"></div> </body> </html>

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Electromagnetic radiation | Spectrum, Examples, & Types | Britannica