Question 742
{"accessible":false,"alternatives":[{"id":3761,"text":"50%"},{"id":3762,"text":"25%"},{"id":3763,"text":"12.5%"},{"id":3764,"text":"6.25%"},{"id":3765,"text":"Not able to be determined"}],"archived":false,"correctAlternativeId":3762,"explanation":"\u003cp\u003eBy passing through two half value layers, the exposure of x-ray photons at the bottom of the container will be 50% ^ 2 = 25% of the exposure at the top of the container surface. If the beam was not monoenergetic, then the relative exposure would not be able to be determined.\u003c/p\u003e\u003cp\u003eAdapted from\u0026nbsp;\u003ca href=\"https://en.wikibooks.org/wiki/Basic_Physics_of_Digital_Radiography\"\u003eBasic Physics of Digital Radiography\u003c/a\u003e\u0026nbsp;by\u0026nbsp;Kieran Maher,\u0026nbsp;with author's permission (License:\u0026nbsp;\u003ca href=\"https://creativecommons.org/licenses/by-sa/3.0/\"\u003eCreative Commons\u0026nbsp;BY-SA 3.0\u003c/a\u003e).\u003c/p\u003e","id":742,"imageUrl":null,"imageAttribution":null,"imageAttributionCaseInfo":null,"firstQuestionPath":"/questions/1194","nextQuestionPath":null,"relatedArticles":[{"id":22271,"title":"Half-value layer","link":"/articles/half-value-layer-1?lang=us"}],"alsoUsedIn":[],"stem":"\u003cp\u003eA narrow beam of monoenergetic x-ray photons is directed from an x-ray tube\u0026nbsp;located 50cm above the surface of a water-filled container 20cm thick. The half value layer for the beam of x-ray photons is 10cm of water. The exposure at the bottom of the container relative to that incident on the surface is about...\u003c/p\u003e","menuLinks":[{"text":"Report problem with question","url":"https://docs.google.com/forms/d/e/1FAIpQLSfO3soWYhOjJ7yErSysyCe5V4A1CqW7WK3rDA7MtAkecMGqNw/viewform?entry.1624461248\u0026entry.553583435=https://radiopaedia.org/questions/742"}],"attemptsPercentages":[{"alternativeId":"3765","percentage":18},{"alternativeId":"3762","percentage":49},{"alternativeId":"3764","percentage":4},{"alternativeId":"3761","percentage":15},{"alternativeId":"3763","percentage":15}],"promptToLogin":false,"questionManager":false,"articleId":"beam-hardening"}