{"id":46,"date":"2022-01-18T16:34:14","date_gmt":"2022-01-18T21:34:14","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/basiclightingforelectricianslevel2\/chapter\/inverse-square-law\/"},"modified":"2022-09-14T15:57:03","modified_gmt":"2022-09-14T19:57:03","slug":"inverse-square-law","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/basiclightingforelectricianslevel2\/chapter\/inverse-square-law\/","title":{"raw":"Inverse Square Law","rendered":"Inverse Square Law"},"content":{"raw":"\nPut simply, the further an object or surface is from a light source, the less light will hit that object or surface. Seems obvious, but it is worth noting that the level of illumination on a surface drops with the square of the distance.\n\n&nbsp;\n<p style=\"text-align: center\">Expressed as an equation:<\/p>\n<p style=\"text-align: center\">[latex]Illumination (lux) =\\frac{Light-intensity (candela)}{distance^2(m)}[\/latex]<\/p>\nExample 1: If 1 Lux of illumination is measured on a surface that is one meter away from a light source, the illumination would be 1\/4th as bright, or \u00bc Lux two meters away, and 1\/9th as bright, or 1\/9th Lux three meters away.\n\n[caption id=\"attachment_48\" align=\"aligncenter\" width=\"640\"]<img class=\"wp-image-47 size-full\" src=\"https:\/\/pressbooks.bccampus.ca\/basiclightingforelectricianslevel2\/wp-content\/uploads\/sites\/1597\/2022\/01\/inverse-square-law.png\" alt=\"\" width=\"640\" height=\"360\"> Illumination of a surface drops with the square of the distance[\/caption]\n\nThis example is a very low value of illumination, but it does illustrate the concept of the inverse square law. A more realistic value of luminous flux density might be around 100 Lux.\n\nExample 2: If 100 Lux of illumination is measured on a surface that is one meter away from a light source, the illumination would be one quarter as bright, or 25 Lux two meters away, and 1\/9th as bright, or 11.1 Lux three meters away, and so on.\n\n<img class=\"aligncenter wp-image-48 size-full\" src=\"https:\/\/pressbooks.bccampus.ca\/basiclightingforelectricianslevel2\/wp-content\/uploads\/sites\/1597\/2022\/01\/inverse-square-law-ex-2.png\" alt=\"\" width=\"640\" height=\"360\">\n","rendered":"<p>Put simply, the further an object or surface is from a light source, the less light will hit that object or surface. Seems obvious, but it is worth noting that the level of illumination on a surface drops with the square of the distance.<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: center\">Expressed as an equation:<\/p>\n<p style=\"text-align: center\">[latex]Illumination (lux) =\\frac{Light-intensity (candela)}{distance^2(m)}[\/latex]<\/p>\n<p>Example 1: If 1 Lux of illumination is measured on a surface that is one meter away from a light source, the illumination would be 1\/4th as bright, or \u00bc Lux two meters away, and 1\/9th as bright, or 1\/9th Lux three meters away.<\/p>\n<figure id=\"attachment_48\" aria-describedby=\"caption-attachment-48\" style=\"width: 640px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-47 size-full\" src=\"https:\/\/pressbooks.bccampus.ca\/basiclightingforelectricianslevel2\/wp-content\/uploads\/sites\/1597\/2022\/01\/inverse-square-law.png\" alt=\"\" width=\"640\" height=\"360\" \/><figcaption id=\"caption-attachment-48\" class=\"wp-caption-text\">Illumination of a surface drops with the square of the distance<\/figcaption><\/figure>\n<p>This example is a very low value of illumination, but it does illustrate the concept of the inverse square law. A more realistic value of luminous flux density might be around 100 Lux.<\/p>\n<p>Example 2: If 100 Lux of illumination is measured on a surface that is one meter away from a light source, the illumination would be one quarter as bright, or 25 Lux two meters away, and 1\/9th as bright, or 11.1 Lux three meters away, and so on.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-48 size-full\" src=\"https:\/\/pressbooks.bccampus.ca\/basiclightingforelectricianslevel2\/wp-content\/uploads\/sites\/1597\/2022\/01\/inverse-square-law-ex-2.png\" alt=\"\" width=\"640\" height=\"360\" \/><\/p>\n","protected":false},"author":848,"menu_order":2,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":["alee59"],"pb_section_license":"all-rights-reserved"},"chapter-type":[],"contributor":[61],"license":[59],"class_list":["post-46","chapter","type-chapter","status-publish","hentry","contributor-alee59","license-all-rights-reserved"],"part":41,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/basiclightingforelectricianslevel2\/wp-json\/pressbooks\/v2\/chapters\/46","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/basiclightingforelectricianslevel2\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/basiclightingforelectricianslevel2\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/basiclightingforelectricianslevel2\/wp-json\/wp\/v2\/users\/848"}],"version-history":[{"count":1,"href":"https:\/\/pressbooks.bccampus.ca\/basiclightingforelectricianslevel2\/wp-json\/pressbooks\/v2\/chapters\/46\/revisions"}],"predecessor-version":[{"id":398,"href":"https:\/\/pressbooks.bccampus.ca\/basiclightingforelectricianslevel2\/wp-json\/pressbooks\/v2\/chapters\/46\/revisions\/398"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/basiclightingforelectricianslevel2\/wp-json\/pressbooks\/v2\/parts\/41"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/basiclightingforelectricianslevel2\/wp-json\/pressbooks\/v2\/chapters\/46\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/basiclightingforelectricianslevel2\/wp-json\/wp\/v2\/media?parent=46"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/basiclightingforelectricianslevel2\/wp-json\/pressbooks\/v2\/chapter-type?post=46"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/basiclightingforelectricianslevel2\/wp-json\/wp\/v2\/contributor?post=46"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/basiclightingforelectricianslevel2\/wp-json\/wp\/v2\/license?post=46"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}