Triple Physics specification mind-map - Radiation in treatment and medicine

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  • Radiation in treatment and medicine
    • Medical Physics
      • CAT scans
        • Imaging device
        • Use a computer to make a 3D image of body
          • Uses images from many different      X-Rays
      • Ultrasounds
        • Lubricant used
        • Detects problems in orans
        • Foetal scanning
      • Endoscopy
        • Optical fibers - thin, flexible glass rods
        • Total internal reflection
        • Through natural openings in body or through small incisions (keyhole surgery)
        • To examine
          • Oesophagus
          • Stomach
          • Colon
          • Respiratory system
          • Urinary tract
          • Reproductive system
      • Radiation
        • Ionising
          • Gamma rays
            • Detect and treat cancers
          • Radioactive sources
            • monitor digestive system
            • Taken into the body and monitored
        • Non-ionising
          • Light in devices which look into the body
    • Lenses
      • Converging
        • Thicker in the middle
          • Bends light inwards
      • Diverging
        • Thinner in the middle
          • Bends light outwards
      • Thicker lenses are more powerful
      • power of lens (dioptre, D) 5 1/focal length (meter, m)
      • 1/f   =   1/u  + 1/v
    • Radiation
      • Any form of energy originating from a source
        • Both waves and particles
      • Intensity
        • Intensity of radiation will decrease with distance from a source
        • Intensity = power of incident radiation / area
          • I = P/A
          • P = I*A
          • A = P/I
    • The Eye
      • Diagram of the eye
      • Light is focused on the retina by the lens and the cornea
      • Human Eye
        • Near point of about  25cm
        • No far point
          • Only restricted by shape of the eye
      • Sight problems
        • Long-sight
          • Cant see up close
        • Short-sight
          • Can't see long distance
        • Correcting sight problems
          • Glasses
            • Short sight
              • Diverging lens
            • Long sight
              • Converging lens
                • Stops light from focusing too soon
          • Contact Lenses
          • Laser eye surgery
            • Short sight
              • Some thickness from central part of cornea removed
                • Reduces focusing power of eye
            • Long sight
              • Curve of cornea increased by removing tissue at its' side
                • Increases focusing power of eye
          • Lenses
            • Converging
              • Thicker in the middle
                • Bends light inwards
            • Diverging
              • Thinner in the middle
                • Bends light outwards
            • Thicker lenses are more powerful
            • power of lens (dioptre, D) 5 1/focal length (meter, m)
            • 1/f   =   1/u  + 1/v
    • Reflection and Refraction
      • Refraction
        • when a wave passes from on medium to another causing a change in speed and direction
      • Reflection
        • Deflection of a ray of light  when it hits the boundary between two different surfaces
        • Total Internal Reflection (TIR)
          • The total internal reflection of light that occurs at the boundary of two materials where the angle of incidence exceeds the critical angle
          • Optical fibers and Endoscopes
            • In an optical fiber, an intense light ray enters a long section of glass at a precise angle to give TIR inside the entire length of glass
            • 2 bundles used
              • One carries light to the object, one back to the eyepiece
          • Total internal reflection

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