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
- X-Rays
- Images can be: REAL or VIRTUAL (can or cannot be projected onto a screen)
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