This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
[{'content': "Determination of Pulp vitality by pulse oximeter based on: \nSelect and explain. \nA. Beer's law., B. Pascal's law., C. Doppler law., D. Poisslues law.", 'role': 'user'}, {'content': 'Answer: A \nExplanation: Pulse oxymetry-\n\nBased on Beer Lambert law\nUtilization of a probe that transmits red (640 mm) and\xa0infrared light\nPhoto detector as a receptor site\nDifferent absorption ability of light by oxygenated and\xa0deoxygenated haemoglobin leads to changes in the\xa0amount of light differently absorbed by the vascular bed\xa0before reaching the photo detector.', 'role': 'assistant'}]