Physics P3 AQA Medical Applications of Physics
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?- Created by: Dominic Hayward
- Created on: 02-05-13 18:59
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- Medical Applications Of Physics
- X-rays
- X-rays are part of the electromagnetic spectrum. They have a short wavelength and cause ionisation
- Properties
- They are transmitted by soft tissue
- Absorbed by metal and bone
- Their wavelength has the diameter of an atom
- They affect a photographic film in the same way as light
- Used to diagnose medical conditions and treat them
- Precuations should be taken as they are ionising
- An example is a C.T scan. They form a three d image as they take slices of x-rays
- Ultrasound
- Higher frequency than human hearing (20-20,000 hertz)
- Ultrasound waves are partially reflected when hitting different densities.
- The time taken for the reflection to reach a detector determines how far away the bondary is.
- s=v*t
- Used in medicine- pre-natal scanning and removing kidney stones.
- Lenses
- Refraction is the change of direction in lightas it passes into a different medium.
- A lense forms an image by refracting light
- In converging/convex lenses parallel rays of light are brought to a focus called the focal length
- refractive index=sini/sinr
- Images; are they real/unreal, magnified/not magnified, upright/inverted
- Converging lense=magnified
- Ray diagrams: through principle axis, through centre and where they meet
- Magnification= image height/object height
- The Eye
- Parts of the eye
- Cornea- Focus' the light
- The lens allows the light to be refracted
- Pupil- allows the light to enter the eye
- The retina- detects light and transmits it to the brain
- The Caliary Muscle- These tighten the thickness
- Suspensory ligaments- these attach the cornea to the claiary muscles
- Concave/Convex lenses help to improve the image on the retina
- Near point- 25cm Far point-infinity
- The eye and a camera work in the same way as they both allow light in and the photographic paper acts in the same way as a retina.
- Power of a lense P=1/f p is dioptres and focal lenght is metres
- Parts of the eye
- Other uses of light
- Total internal reflection- refractive index=1/sinc
- Crotical angle is where the refracted ray disappears
- Light can be sent along optical fibres
- Endoscopes send light down a tube in order to see.
- Makes surgery much easier
- Endoscopes send light down a tube in order to see.
- Lasers can be used for cutting,cauterising and burning
- X-rays
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