Medical Physics

Eye, X-rays, Ultrasound, Lenses

  • Created by: cherryXX
  • Created on: 09-03-14 15:13
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  • Medical Physics
    • X-Rays
      • Short wave length
      • Cause Ionisation in cells and can KILL them
      • Absorbed by bone and metal
      • Transmitted by healthy tissues (PASS THROUGH)
      • Useful for diagnosis in medical science
      • Used in medical imaging to see things such as bone fractures and dental problems
      • CCDs, Charged Couples Devise
      • CT Scans, Computerised Tomography
      • CCDs= Electronically Charged images
      • CT Scans= 2D images prossed to make a 3D image
      • Precations to reduce ionisation need to be taken by RADIOGRAPHERS
        • Leave the room
        • Stand behind LEAD screen
        • Wear LEAD aprons
        • Lead can act as protective layers
    • Ultrasound
      • VERY HIGH FREQUENCY ABOVE 20,000 Hz (Hertz)...too high for humans to hear
      • Reflects of media when it reaches new surfaces with a different density.
      • S=VT Distance= velocityXtime
      • Distance measured in Meters...Speed (Velocity) measeured in M/S...Time measured in Secounds
      • Can be used for MEDICAL USES
      • Pre-natal scanning Checks develpment of Foetus and takeing measurements
      • Breaking Kidney Stones
      • Ultrasound ISN'T Ionising
    • Lenses
      • Diverging Lenses
      • Converging Lenses
      • Converging lens curved outwards
      • Converging lenses refract these parallel rays so that they are come together at a point called the principal focus
      • Converging=REAL IMAGE
      • A diverging lens is curved inwards on both sides
      • form a virtual image - an image that cannot be projected onto a screen.
      • Images can be: MAGNIFIED or DIMINISHED (bigger or smaller)
      • Images can be: UPRIGHT or INVERTED (right way up or upside down)
      • Images can be: REAL or VIRTUAL (can or cannot be projected onto a screen)
    • Eye
      • Cornea=  Refracts light as it enters the eye (by a fixed amount).
      • Iris= Controls how much light enters the pupil.
      • Pupil= Allows light to pass through as it enters the eye.
      • Lens= Refracts light to focus it onto the retina. The amount of refraction can be adjusted by altering the thickness and curvature of the lens.
      • Ciliary Muscles= Adjust the shape of the lens to make it more or less curved, so as to increase or decrease the refraction of light
      • Suspensory Ligaments=   Slacken or stretch as the ciliary muscles contract or relax, to adjust the thickness and curvature of the lens.
      • Retina= Contains the light receptors, which trigger electrical impulses to be sent to the brain when light is detected.
      • Near Point is the closest an object can be from the eye without the object appearing blurred.
      • Someone with long sight can see distant objects clearly, but their point is further away than 25 cm. This means they cannot focus properly on objects.
      • The far point is the furthest an object can be from the eye without it appearing blurred.
      • Someone with short sight can see near objects clearly, but their far point is closer than infinity. This means they cannot focus properly on distant objects.
      • Comparison between the EYE and a CAMERA:  lens focuses light,  focuses on distent objects
  • Images can be: REAL or VIRTUAL (can or cannot be projected onto a screen)


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