{"id":4466,"date":"2017-03-29T16:17:22","date_gmt":"2017-03-29T16:17:22","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/wm-biology2\/?post_type=chapter&#038;p=4466"},"modified":"2024-04-26T02:20:29","modified_gmt":"2024-04-26T02:20:29","slug":"light","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/wm-biology2\/chapter\/light\/","title":{"raw":"Light","rendered":"Light"},"content":{"raw":"<div class=\"textbox learning-objectives\">\r\n<h3>Learning Outcomes<\/h3>\r\n<ul>\r\n \t<li>Explain how electromagnetic waves differs from sound waves<\/li>\r\n<\/ul>\r\n<\/div>\r\nAs with auditory stimuli, light travels in waves. The compression waves that compose sound must travel in a medium\u2014a gas, a liquid, or a solid. In contrast, light is composed of electromagnetic waves and needs no medium; light can travel in a vacuum (Figure\u00a01). The behavior of light can be discussed in terms of the behavior of waves and also in terms of the behavior of the fundamental unit of light\u2014a packet of electromagnetic radiation called a photon. A glance at the electromagnetic spectrum shows that visible light for humans is just a small slice of the entire spectrum, which includes radiation that we cannot see as light because it is below the frequency of visible red light and above the frequency of visible violet light.\r\n\r\nCertain variables are important when discussing perception of light. Wavelength (which varies inversely with frequency) manifests itself as hue. Light at the red end of the visible spectrum has longer wavelengths (and is lower frequency), while light at the violet end has shorter wavelengths (and is higher frequency). The wavelength of light is expressed in nanometers (abbreviated nm); one nanometer is one billionth of a meter. Humans perceive light that ranges between approximately 380 nm and 740 nm. Some other animals, though, can detect wavelengths outside of the human range. For example, bees see near-ultraviolet light in order to locate nectar guides on flowers, and some non-avian reptiles sense infrared light (heat that prey gives off).\r\n\r\n[caption id=\"attachment_2720\" align=\"aligncenter\" width=\"1024\"]<img class=\"size-large wp-image-2720\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/02\/07215643\/Figure_36_05_01-1024x433.jpg\" alt=\"The illustration shows the electromagnetic spectrum, which consists of different wavelengths of electromagnetic radiation. Radio waves have the longest wavelength, about 103 meters. Wavelength gets increasingly shorter for microwave, infrared, visible, ultraviolet, x-rays and gamma rays. Gamma rays have a wavelength of about 10-12 meters. Frequency is inversely proportional to wavelength.\" width=\"1024\" height=\"433\" \/> Figure\u00a01.\u00a0In the electromagnetic spectrum, visible light lies between 380 nm and 740 nm. (credit: modification of work by NASA)[\/caption]\r\n\r\nWave amplitude is perceived as luminous intensity, or brightness. The standard unit of intensity of light is the <b>candela<\/b>, which is approximately the luminous intensity of a one common candle.\r\n\r\nLight waves travel 299,792 km per second in a vacuum, (and somewhat slower in various media such as air and water), and those waves arrive at the eye as long (red), medium (green), and short (blue) waves. What is termed \u201cwhite light\u201d is light that is perceived as white by the human eye. This effect is produced by light that stimulates equally the color receptors in the human eye. The apparent color of an object is the color (or colors) that the object reflects. Thus a red object reflects the red wavelengths in mixed (white) light and absorbs all other wavelengths of light.\r\n<div class=\"textbox tryit\">\r\n<h3>Try It<\/h3>\r\nhttps:\/\/assess.lumenlearning.com\/practice\/6fbbac17-f4ca-42b3-b527-9d3f8c92b0aa\r\n<\/div>","rendered":"<div class=\"textbox learning-objectives\">\n<h3>Learning Outcomes<\/h3>\n<ul>\n<li>Explain how electromagnetic waves differs from sound waves<\/li>\n<\/ul>\n<\/div>\n<p>As with auditory stimuli, light travels in waves. The compression waves that compose sound must travel in a medium\u2014a gas, a liquid, or a solid. In contrast, light is composed of electromagnetic waves and needs no medium; light can travel in a vacuum (Figure\u00a01). The behavior of light can be discussed in terms of the behavior of waves and also in terms of the behavior of the fundamental unit of light\u2014a packet of electromagnetic radiation called a photon. A glance at the electromagnetic spectrum shows that visible light for humans is just a small slice of the entire spectrum, which includes radiation that we cannot see as light because it is below the frequency of visible red light and above the frequency of visible violet light.<\/p>\n<p>Certain variables are important when discussing perception of light. Wavelength (which varies inversely with frequency) manifests itself as hue. Light at the red end of the visible spectrum has longer wavelengths (and is lower frequency), while light at the violet end has shorter wavelengths (and is higher frequency). The wavelength of light is expressed in nanometers (abbreviated nm); one nanometer is one billionth of a meter. Humans perceive light that ranges between approximately 380 nm and 740 nm. Some other animals, though, can detect wavelengths outside of the human range. For example, bees see near-ultraviolet light in order to locate nectar guides on flowers, and some non-avian reptiles sense infrared light (heat that prey gives off).<\/p>\n<div id=\"attachment_2720\" style=\"width: 1034px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-2720\" class=\"size-large wp-image-2720\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/02\/07215643\/Figure_36_05_01-1024x433.jpg\" alt=\"The illustration shows the electromagnetic spectrum, which consists of different wavelengths of electromagnetic radiation. Radio waves have the longest wavelength, about 103 meters. Wavelength gets increasingly shorter for microwave, infrared, visible, ultraviolet, x-rays and gamma rays. Gamma rays have a wavelength of about 10-12 meters. Frequency is inversely proportional to wavelength.\" width=\"1024\" height=\"433\" \/><\/p>\n<p id=\"caption-attachment-2720\" class=\"wp-caption-text\">Figure\u00a01.\u00a0In the electromagnetic spectrum, visible light lies between 380 nm and 740 nm. (credit: modification of work by NASA)<\/p>\n<\/div>\n<p>Wave amplitude is perceived as luminous intensity, or brightness. The standard unit of intensity of light is the <b>candela<\/b>, which is approximately the luminous intensity of a one common candle.<\/p>\n<p>Light waves travel 299,792 km per second in a vacuum, (and somewhat slower in various media such as air and water), and those waves arrive at the eye as long (red), medium (green), and short (blue) waves. What is termed \u201cwhite light\u201d is light that is perceived as white by the human eye. This effect is produced by light that stimulates equally the color receptors in the human eye. The apparent color of an object is the color (or colors) that the object reflects. Thus a red object reflects the red wavelengths in mixed (white) light and absorbs all other wavelengths of light.<\/p>\n<div class=\"textbox tryit\">\n<h3>Try It<\/h3>\n<p>\t<iframe id=\"assessment_practice_6fbbac17-f4ca-42b3-b527-9d3f8c92b0aa\" class=\"resizable\" src=\"https:\/\/assess.lumenlearning.com\/practice\/6fbbac17-f4ca-42b3-b527-9d3f8c92b0aa?iframe_resize_id=assessment_practice_id_6fbbac17-f4ca-42b3-b527-9d3f8c92b0aa\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:300px;\"><br \/>\n\t<\/iframe>\n<\/div>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-4466\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Biology 2e. <strong>Provided by<\/strong>: OpenStax. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\">http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em>. <strong>License Terms<\/strong>: Access for free at https:\/\/openstax.org\/books\/biology-2e\/pages\/1-introduction<\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section>","protected":false},"author":17,"menu_order":18,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Biology 2e\",\"author\":\"\",\"organization\":\"OpenStax\",\"url\":\"http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"Access for free at https:\/\/openstax.org\/books\/biology-2e\/pages\/1-introduction\"}]","CANDELA_OUTCOMES_GUID":"41bb77de-b447-40da-a860-bb9524753729, 3657b1f5-b78a-4ee7-be7c-1d4fcf2cf407","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-4466","chapter","type-chapter","status-publish","hentry"],"part":3798,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters\/4466","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/users\/17"}],"version-history":[{"count":7,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters\/4466\/revisions"}],"predecessor-version":[{"id":8595,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters\/4466\/revisions\/8595"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/parts\/3798"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters\/4466\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/media?parent=4466"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapter-type?post=4466"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/contributor?post=4466"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/license?post=4466"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}