e39465ad2f
new file: Files/flashplayer_32_sa.exe
new file: favicon.ico
new file: globe.gif
new file: imgs/download.png
new file: imgs/zuck.jpg
new file: index.html
new file: other.ico
new file: script.js
new file: site.webmanifest
new file: sitemap.html
new file: styles/backround.css
new file: styles/border.css
new file: styles/fonts/Titillium_Web/OFL.txt
new file: styles/fonts/Titillium_Web/TitilliumWeb-Black.ttf
new file: styles/fonts/Titillium_Web/TitilliumWeb-Bold.ttf
new file: styles/fonts/Titillium_Web/TitilliumWeb-BoldItalic.ttf
new file: styles/fonts/Titillium_Web/TitilliumWeb-ExtraLight.ttf
new file: styles/fonts/Titillium_Web/TitilliumWeb-ExtraLightItalic.ttf
new file: styles/fonts/Titillium_Web/TitilliumWeb-Italic.ttf
new file: styles/fonts/Titillium_Web/TitilliumWeb-Light.ttf
new file: styles/fonts/Titillium_Web/TitilliumWeb-LightItalic.ttf
new file: styles/fonts/Titillium_Web/TitilliumWeb-Regular.ttf
new file: styles/fonts/Titillium_Web/TitilliumWeb-SemiBold.ttf
new file: styles/fonts/Titillium_Web/TitilliumWeb-SemiBoldItalic.ttf
new file: styles/fonts/webfontkit-20221027-163353/generator_config.txt
new file: styles/fonts/webfontkit-20221027-163353/specimen_files/grid_12-825-55-15.css
new file: styles/fonts/webfontkit-20221027-163353/specimen_files/specimen_stylesheet.css
new file: styles/fonts/webfontkit-20221027-163353/stylesheet.css
new file: styles/fonts/webfontkit-20221027-163353/titilliumweb-extralight-demo.html
new file: styles/fonts/webfontkit-20221027-163353/titilliumweb-extralight-webfont.woff
new file: styles/fonts/webfontkit-20221027-163353/titilliumweb-extralight-webfont.woff2
new file: styles/fonts/webfontkit-20221027-165950/generator_config.txt
new file: styles/fonts/webfontkit-20221027-165950/specimen_files/grid_12-825-55-15.css
new file: styles/fonts/webfontkit-20221027-165950/specimen_files/specimen_stylesheet.css
new file: styles/fonts/webfontkit-20221027-165950/stylesheet.css
new file: styles/fonts/webfontkit-20221027-165950/titilliumweb-bold-demo.html
new file: styles/fonts/webfontkit-20221027-165950/titilliumweb-bold-webfont.woff
new file: styles/fonts/webfontkit-20221027-165950/titilliumweb-bold-webfont.woff2
new file: styles/style.css
new file: tools/2048/.gitignore
new file: tools/2048/.jshintrc
new file: tools/2048/CONTRIBUTING.md
new file: tools/2048/LICENSE.txt
new file: tools/2048/README.md
new file: tools/2048/Rakefile
new file: tools/2048/favicon.ico
new file: tools/2048/index.html
new file: tools/2048/js/animframe_polyfill.js
new file: tools/2048/js/application.js
new file: tools/2048/js/bind_polyfill.js
new file: tools/2048/js/classlist_polyfill.js
new file: tools/2048/js/game_manager.js
new file: tools/2048/js/grid.js
new file: tools/2048/js/html_actuator.js
new file: tools/2048/js/keyboard_input_manager.js
new file: tools/2048/js/local_storage_manager.js
new file: tools/2048/js/tile.js
new file: tools/2048/meta/apple-touch-icon.png
new file: tools/webretro/cores/neocd_libretro.js
new file: tools/webretro/cores/neocd_libretro.wasm
new file: tools/webretro/cores/nestopia_libretro.js
new file: tools/webretro/cores/nestopia_libretro.wasm
new file: tools/webretro/cores/o2em_libretro.js
new file: tools/webretro/cores/o2em_libretro.wasm
new file: tools/webretro/cores/opera_libretro.js
new file: tools/webretro/cores/opera_libretro.wasm
208 lines
10 KiB
HTML
208 lines
10 KiB
HTML
<!DOCTYPE html>
|
|
<html lang="en"><!-- #BeginTemplate "/Templates/Advanced.dwt" --><!-- DW6 -->
|
|
|
|
<!-- Mirrored from www.mathsisfun.com/physics/waves-radio-microwave.html by HTTrack Website Copier/3.x [XR&CO'2014], Sat, 29 Oct 2022 00:51:05 GMT -->
|
|
<head>
|
|
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
|
|
|
|
|
|
<!-- #BeginEditable "doctitle" -->
|
|
<title>Radio Waves and Microwaves</title>
|
|
<meta name="description" content="Math explained in easy language, plus puzzles, games, quizzes, videos and worksheets. For K-12 kids, teachers and parents.">
|
|
|
|
|
|
<script>reSpell=[["millimeter","millimetre"],["centimeter","centimetre"],["centimeters","centimetres"],["kilometers","kilometres"]];</script>
|
|
|
|
<!-- #EndEditable -->
|
|
<meta name="keywords" content="math, maths, mathematics, school, homework, education">
|
|
<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
|
|
<meta name="HandheldFriendly" content="true">
|
|
<meta name="referrer" content="always">
|
|
<link rel="preload" href="../images/style/font-champ-bold.ttf" as="font" type="font/ttf" crossorigin="">
|
|
<link rel="preload" href="../style4.css" as="style">
|
|
<link rel="preload" href="../main4.js" as="script">
|
|
<link rel="stylesheet" href="../style4.css">
|
|
<script src="../main4.js" defer="defer"></script>
|
|
<!-- Global site tag (gtag.js) - Google Analytics -->
|
|
<script async="" src="https://www.googletagmanager.com/gtag/js?id=UA-29771508-1"></script>
|
|
<script>
|
|
window.dataLayer = window.dataLayer || [];
|
|
function gtag(){dataLayer.push(arguments);}
|
|
gtag('js', new Date());
|
|
gtag('config', 'UA-29771508-1');
|
|
</script>
|
|
</head>
|
|
|
|
<body id="bodybg" class="adv">
|
|
|
|
<div id="stt"></div>
|
|
<div id="adTop"></div>
|
|
<header>
|
|
<div id="hdr"></div>
|
|
<div id="tran"></div>
|
|
<div id="adHide"></div>
|
|
<div id="cookOK"></div>
|
|
</header>
|
|
|
|
<div class="mid">
|
|
|
|
<nav>
|
|
<div id="menuWide" class="menu"></div>
|
|
<div id="logo"><a href="../index.html"><img src="../images/style/logo-adv.svg" alt="Math is Fun Advanced"></a></div>
|
|
|
|
<div id="search" role="search"></div>
|
|
<div id="linkto"></div>
|
|
|
|
<div id="menuSlim" class="menu"></div>
|
|
<div id="menuTiny" class="menu"></div>
|
|
</nav>
|
|
|
|
<div id="extra"></div>
|
|
|
|
<article id="content" role="main">
|
|
|
|
<!-- #BeginEditable "Body" -->
|
|
|
|
|
|
<h1 class="center">Radio Waves and Microwaves</h1>
|
|
|
|
<p class="center"><img src="images/phone-mobile.jpg" alt="phone mobile" height="167" width="480"></p>
|
|
<p class="center large">Radio waves and microwaves are very important to us for <b>communication</b>.</p>
|
|
<p class="center"><i><br></i>
|
|
<img src="images/microwave.svg" alt="microwave" height="98" width="162"><i><br>And for heating up left over pizza!</i></p>
|
|
|
|
|
|
<h2>Electromagnetic</h2>
|
|
|
|
<p>They are both on the <b>long wavelength</b> end of the <a href="electromagnetic-spectrum.html">Electromagnetic Spectrum</a>:</p>
|
|
|
|
<div class="script" style="height: 260px;">
|
|
images/em-spectrum.js
|
|
</div>
|
|
|
|
|
|
<p> </p>
|
|
<ul>
|
|
<li>Radio waves have wavelengths of <b>1 m</b> up.<br>
|
|
The frequency at 1 m is 300 MHz.</li>
|
|
<li>Microwaves have wavelengths of <b>1 mm</b> (millimeter) to <b>1 m</b>.<br>
|
|
The frequency at 1 mm is 300 GHz.</li>
|
|
</ul>
|
|
<p>(Note: some people say microwaves are just a type of radio wave, so for them radio waves have wavelengths of <b>1 mm</b> up.)</p>
|
|
<p>We can create radio and microwaves, and they are also produced by the Sun and many other natural sources.</p>
|
|
|
|
|
|
<h2>Wireless Communication</h2>
|
|
|
|
<p>We use radio and microwaves to communicate without wires. This is great, as we can move around and live our lives while still being in touch.</p>
|
|
|
|
|
|
<h2>Transmitting and Receiving</h2>
|
|
|
|
<p class="center"><img src="images/radio-mobile-phone.svg" alt="radio mobile phone" height="" width=""><br>
|
|
Transmit ... and Receive on a device</p>
|
|
<p>Radio waves are produced by a vibrating electric current in an antenna ...</p>
|
|
<p class="center">... the <a href="electromagnetic-spectrum.html">electromagnetic</a> waves then spread out ...</p>
|
|
<p>... and are then received by a small antenna inside your device, that detects the very small amount of current created by the radio waves.</p>
|
|
<p>Your device can then decode the signal, and you can watch or listen to what was sent out.</p>
|
|
|
|
|
|
<h2>Broadcasting</h2>
|
|
|
|
<p>Radio waves are good at <b>broad</b>casting (sending out to lots of receivers) and that is how we get to listen to radio and TV broadcasts.</p>
|
|
<p class="center"><img src="images/antenna-tv.svg" alt="antenna tv" height="" width=""><br>
|
|
TVs (and radios!) can receive <b>broadcast</b> signals using antennas.</p>
|
|
<p>Radio waves are good at bending around buildings and hills by <a href="diffraction.html">diffraction</a> (see below also).</p>
|
|
|
|
|
|
<h2>Microwave Ovens</h2>
|
|
|
|
<p>Microwave ovens use electromagnetic waves at a frequency of <i><b>2.45 GHz</b> (wavelength about 12 cm)</i> that make water molecules vibrate fast and heat up.</p>
|
|
<p class="center"><img src="images/microwave-works.svg" alt="microwave magnetron, stirrer and pie absorbs" height="208" width="304"><br>
|
|
Microwaves are created by the Magnetron,<br>
|
|
are sent in different directions by the stirrer,<br>
|
|
bounce off metal surfaces,<br>
|
|
and are absorbed by the water in food.</p>
|
|
<p>Microwaves can travel through glass and plastic and penetrate about a centimeter into food (depending on the food), but bounce off metal surfaces.</p>
|
|
<p>There must always be <b>something to absorb the microwaves</b>, such as food or a glass of water.</p>
|
|
<p>So basically you are cooking by heating up the water in the first cm or so of the food. That is why many recipes say to leave the food stand for a while (to let the heat spread evenly).</p>
|
|
<p>Microwaves can also heat <b>us</b> up and can <b>damage</b> our cells. Keep the door closed when on, and never use a damaged microwave oven.</p>
|
|
<p> </p>
|
|
<p style="float:right; margin: 0 0 5px 10px;"><img src="images/diffraction-harbor.jpg" alt="diffraction waves in harbor" height="300" width="202"><br>
|
|
Wave diffraction into a bay</p>
|
|
|
|
|
|
<h2><span class="center">Diffraction</span></h2>
|
|
|
|
<p><a href="diffraction.html">Diffraction</a> is very important for radio communications!</p>
|
|
<p class="larger">Diffraction is when waves <b>bend around the corner</b> of an obstacle.</p>
|
|
<p style="float:left; margin: 0 10px 5px 0;"><img src="images/diffractions.gif" alt="diffraction wave behaviour" height="260" width="129"></p>
|
|
<p> </p>
|
|
<p>Medium gap: <i>some diffraction, but mostly straight</i></p>
|
|
<p> </p>
|
|
<p> </p>
|
|
<p>Gap of <b>wavelength</b> size: <i>most diffraction</i></p>
|
|
<p> </p>
|
|
<p>The maximum effect is when the gap and wavelength are about the same size.</p>
|
|
<p class="center"><img src="images/wave-diffraction-radio.svg" alt="wave diffraction radio" height="" width=""><br>
|
|
<b>Radio waves</b> with wavelengths of <b>kilometers</b> diffract<br>
|
|
over hills and through valleys so you can easily get reception.</p>
|
|
<p class="center"><img src="images/wave-diffraction-micro.svg" alt="wave diffraction microwave" height="" width=""><br>
|
|
But microwaves with wavelength of <b>centimeters</b> mostly go straight.</p>
|
|
<p style="float:right; margin: 0 0 5px 10px;"><img src="images/microwave-dish-tower.jpg" alt="microwave dish tower" height="400" width="135"></p>
|
|
<p> </p>
|
|
<p> </p>
|
|
<p>So radio waves are good at "<b>broad</b>casting" to many people, but microwaves are good at point-to-point communication.</p>
|
|
<p>And for microwaves the transmitter and receiver must be "line of sight" (they can see each other).</p>
|
|
<p>A typical microwave antenna is a <a href="../geometry/parabola.html">parabolic</a> dish of about 0.3 m to 3 m in diameter, like on this building:</p>
|
|
<p> </p>
|
|
|
|
|
|
<h2> </h2>
|
|
|
|
<h2>Ionosphere</h2>
|
|
|
|
<p>The ionosphere is an electrically charged layer of the upper atmosphere that is between 75 and 1000 km above the ground.</p>
|
|
<p>It is very important for radio and microwave communication!</p>
|
|
<p>Low to medium frequency radio waves get reflected off the ionosphere, so it is possible to receive radio signals from far away that have bounced their way to us.</p>
|
|
<p class="center"><img src="images/radio-microwaves-earth.svg" alt="radio microwaves earth" height="366" width="702"><br>
|
|
<i>(Not to scale)</i></p>
|
|
<p>But microwaves can cut right through the ionosphere so they are good for communicating with satellites.</p>
|
|
|
|
|
|
<h2>Signal and Noise</h2>
|
|
|
|
<p class="center"><img src="../data/images/analog-digital.svg" alt="analog digital" height="161" width="360"><br>
|
|
Information can be in <a href="../data/analog-digital.html">analog or digital</a> form.</p>
|
|
|
|
<h3>Analog</h3>
|
|
<p>Information can be put onto a wave by altering its height or wavelength a little:</p>
|
|
<p class="center"><img src="../data/images/analog-picture.jpg" alt="analog picture" height="100" width="422"><br>
|
|
A wave has a <b>signal</b> of this picture put into it.</p>
|
|
<p>As the wave travels it gets <b>noise</b> (random changes) added by other electrical activity around it:</p>
|
|
<p class="center"><img src="../data/images/analog-picture-noise.jpg" alt="analog picture noise" height="100" width="280"><br>
|
|
When we try to recreate the image the result is not perfect!</p>
|
|
|
|
<h3>Digital</h3>
|
|
<p>But with digital we expect <b>only certain values</b>, such as 0s or 1s. So noise (if not too big) can be overcome.</p>
|
|
<p class="center"><img src="../data/images/digital-picture-noise.jpg" alt="digital picture noise does not affect quality" height="100" width="423"><br>
|
|
Even with noise we still know every 0 and 1 and get a perfect image.</p>
|
|
<p> </p>
|
|
<div class="questions">17751, 17753, 17754, 17758</div>
|
|
|
|
<div class="related">
|
|
<a href="electromagnetic-spectrum.html">Electromagnetic Spectrum</a>
|
|
<a href="index.html">Physics Index</a>
|
|
</div>
|
|
<!-- #EndEditable -->
|
|
|
|
</article>
|
|
|
|
<div id="adend" class="centerfull noprint"></div>
|
|
<footer id="footer" class="centerfull noprint"></footer>
|
|
<div id="copyrt">Copyright © 2021 Rod Pierce</div>
|
|
|
|
</div>
|
|
</body><!-- #EndTemplate -->
|
|
<!-- Mirrored from www.mathsisfun.com/physics/waves-radio-microwave.html by HTTrack Website Copier/3.x [XR&CO'2014], Sat, 29 Oct 2022 00:51:08 GMT -->
|
|
</html> |