{"id":90,"date":"2015-07-30T13:32:13","date_gmt":"2015-07-30T17:32:13","guid":{"rendered":"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/lab6\/physics-1140-lab-6-interference-of-light-from-a-laser\/"},"modified":"2020-09-02T09:37:19","modified_gmt":"2020-09-02T13:37:19","slug":"backgroundinterference-of-light-from-a-laser","status":"publish","type":"page","link":"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/physics-1140-lab-6-interference-of-light-from-a-laser-4\/backgroundinterference-of-light-from-a-laser\/","title":{"rendered":"Lab 6: Background"},"content":{"rendered":"<h2>Interference at a point<\/h2>\n<ul>\n<li>When do waves interfere?\n<ul>\n<li>Waves from 2 or more identical sources pass through the same region of space<\/li>\n<\/ul>\n<\/li>\n<li>What is the total disturbance?\n<ul>\n<li>Use the principle of superposition.<\/li>\n<li>The total disturbance at a point is the sum of the disturbances from each source alone.<\/li>\n<li>The result can be larger or smaller than the individual waves, depending on the relative phase.<\/li>\n<\/ul>\n<\/li>\n<li>Constructive Interference\n<ul>\n<li>Crests coincide with crests.<\/li>\n<li>Troughs coincide with troughs.<\/li>\n<li>Waves are &#8220;in phase&#8221;.<\/li>\n<li>The resulting disturbance has twice the amplitude of the individual waves&#8230;<\/li>\n<li>&#8230;assuming two sources emitting waves of equal amplitude<\/li>\n<\/ul>\n<\/li>\n<li>Destructive Interference\n<ul>\n<li>Crests coincide with troughs.<\/li>\n<li>Waves are &#8220;180\u00b0 out of phase&#8221;.<\/li>\n<li>Zero total disturbance&#8230;<\/li>\n<li>&#8230;again assuming two sources emitting waves of equal amplitude<\/li>\n<\/ul>\n<\/li>\n<li>Constructive and destructive interference are just the extreme cases.\n<ul>\n<li>Smooth variation from one to the other<\/li>\n<li>&#8220;Partially out of phase&#8221;<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h2>Interference Patterns<\/h2>\n<ul>\n<li>What is an interference pattern?\n<ul>\n<li>Interference that is stable in time at each point in a region of space, creating an observable pattern of maxima (constructive interference, large amplitudes) and minima (destructive interference, small amplitudes)<\/li>\n<\/ul>\n<\/li>\n<li>Require &#8220;coherent&#8221; sources\n<ul>\n<li>Same frequency<\/li>\n<li>Constant phase relationship<\/li>\n<\/ul>\n<\/li>\n<li>It&#8217;s not hard to make physically distinct sources of water waves or sound waves coherent.<\/li>\n<li>It&#8217;s very hard to do this with sources of visible light waves&#8230;<\/li>\n<li>&#8230;so take light from one source and create several different sources by sending the light on different paths before allowing it to interfere.<\/li>\n<li>This is most easily done with bright, monochromatic (single frequency) sources of light with good phase stability&#8230;<\/li>\n<li>&#8230;so we will use <a href=\"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/physics-1140-lab-6-interference-of-light-from-a-laser-4\/lab-6-equipment\/#LaserPointer\">lasers<\/a> as our light sources in this lab.<\/li>\n<\/ul>\n<p><a href=\"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/physics-1140-lab-6-interference-of-light-from-a-laser-4\/lab-6-equipment\/\">Equipment<\/a> <a href=\"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/physics-1140-lab-6-interference-of-light-from-a-laser-4\/lab-6-dtat-collection-and-analysis\/\">Data Collection and Analysis<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Interference at a point When do waves interfere? Waves from 2 or more identical sources pass through the same region of space What is the total disturbance? Use the principle of superposition. The total disturbance at a point is the sum of the disturbances from each source alone. The result can be larger or smaller [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"parent":93,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-90","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/wp-json\/wp\/v2\/pages\/90","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/wp-json\/wp\/v2\/comments?post=90"}],"version-history":[{"count":0,"href":"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/wp-json\/wp\/v2\/pages\/90\/revisions"}],"up":[{"embeddable":true,"href":"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/wp-json\/wp\/v2\/pages\/93"}],"wp:attachment":[{"href":"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/wp-json\/wp\/v2\/media?parent=90"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}