Medical uses of light

P3 Topic 6 CGP book

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Endoscope: Thin tube containing opical fibres

  • 1 to carry light -1 to carry an image back
  • Image seen on eyepiece or screen
  • called Key Hole surgary, good as doctors only need to cut a tiny hole


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Pulse Oximeter

Pules oximeters use light to check the oxygen levels in the blood 

Haemoglobian carries oxygen from lungs to cells. It changes colour due oxygen content. Lots of oxygen - Red (oxyhaemoglobian) Lackign oxygen - Purply(reduced haemoglobin

How it works

  • Trasmitter emits two beams of light (red & infared). It also has a photo detector to measure light.
  • These are placed either side of the finger (or ear lobe etc)
  • Beams of light are passed through the finger, some of the light is then absorbed by the blood.
  • It is the difference in light intensity before the light passes through the blood, and after, that is used to measure the oxygen levels in the blood    (
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