What types of methods do physicians use to solve medical problems?
CAT-scanners, Utrasound, Endoscopes, Ionising and non-ionsing radiation.
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How do CAT scanners work?
X-rays are absorbed by some materials inside the body but not others. A negative image is produced.
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How does Ultrasound work?
High frequency sound waves reflect off features inside the body to form an image (ultrasound scanners)
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How do endoscopes work?
Visible light reflects off features to form an image.
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How does ionising and non-ionising radiation work?
X-rays and gamma rays are used to destroy cancer cells, light and ultrasound are used - lasers are used in eye surgery to correct vision defects. Absorption of ultrasound helps treat swollen tissue.
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What is radiation?
Radiation is any form of energy originating from a source - including rays and particles.
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How does the intensity of radiation change?
Intensity of radiation will be stronger nearer the source and it will decrease with distance. This is according to the nature of the medium it travels through.
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Intensity equation?
power of incident radiation/area
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Features of an eye?
Cornea, iris, pupil, lens, retina, ciliary muscle
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How is light focused in the eye?
Light is focused in the eye as it passes through the cornea, the pupil and into the lens. It focuses on the retina.
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What is the near and far point?
The furthest you can see an image (infinity) and the closest you can see a focused image (25cm).
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Causes of short sight?
Either the eyeball being too long or the cornea being curved too sharply.
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Causes of long sight?
Eye ball being too short, lens not being thick enough or curved enough.
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Simple lens treatment
Short sight can be corrected by glasses with diverging lenses. This bends incoming rays so they can focus on the retina. Long sight cured by converging lenses which refracts rays more so they can focus on the retina.
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Contact lens treatment
Placed on front of cornea. Some are softer than others but all allow oxygen to permeate the eye. Must be cleaned regularly.
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Laser correction treatment
Uses finely controlled laser to reshape the front of the cornea. The laser can make precise incisions without damaging surrounding tissue.
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How diverging and converging lenses refract light
Diverging lenses have a focal point before the lens (it is negative) - rays go outwards through lens. Converging lenses have positive focal point.
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Power of lens (dioptre) equation
1/focal length in m
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Lens equation
1/f = 1/u + 1/v (u is object distance, v is image distance and f is focal length)
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Reflection
Law of reflection is angle of incidence = angle of reflection
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Snell's law
Snell's law links angles of incidence and refraction for waves passing through one medium to another. Sinxi/sinxr = constant.
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How is TIR used in optical fibres?
It guides the light ray right to the end (the twisty tube) so you can see the image.
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Use of optical fibres in endoscopes
The endoscope consists of optical fibres in a flexible rod. Some fibres carry light in them. Light if reflected off the inside of the body, gathered and focused to form a clear image at the lens.
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Uses of ultrasound in diagnosis and treatment
Ultrasound can help locate kidney stones. Absorption of ultrasound can help treat injured muscles.
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Other cards in this set
Card 2
Front
How do CAT scanners work?
Back
X-rays are absorbed by some materials inside the body but not others. A negative image is produced.
Card 3
Front
How does Ultrasound work?
Back
Card 4
Front
How do endoscopes work?
Back
Card 5
Front
How does ionising and non-ionising radiation work?
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