The part of the electromagnectic spectrum. High frequency and very short wave length.
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CCDs
Used to form electronic images of x-rays.
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CT Scanners
They use x-rays to produce digital imaged oof a cross section through the body.
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Ultrasound waves
Sound waves with a higher freequency of 20 000hz.
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Refraction
Change of direction of light as it passes from one transparent substance into another.
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Refractive Index
A measure of how much the substance can refract a light ray.
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Total internal refraction
If the angle of incidence is beyond the critical angle the light ray undergoes total internal refraction.
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Edoscope
A device used to look inside a paitents body without cutting it. It contains optical fibres; very thin glass fibers. Visual light can be sent down by total internal refraction.
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Converging lens
Parallel rays of light pass through this and converge at one point; the principle focus. The distance from the centre of the lens to the principle focus is the focal length.
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Real image
When the object is further away from the lens than the principle focus, an inverted, real image is formed.
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Virtual Image
If an object is nearer to the lens than the principle focus, an upright, virtual image is formed behind the object. The image is magnified and the lens acts like a magnifying glass.
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Magnification
Magnification = Image height / Object height
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Diverging lens
Parallel rays of light pass through this and are refracted. They diverge from a point.
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Principle axis
The line through the centre of the lens and at right angles to it
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Cornea
transparent layer that protects the eye and helps to focus light onto the retina
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Retina
Light sensitive cells around the inside of the eye
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Iris
Coloured ring of muscle that controls amount of light entering the eye.
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Ciliary muscles
attaches to the lens by suspensory ligaments. The muscles change the thickness of the eye lens.
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Short sight
When the rays of light meet before touching the back of the retina
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Long sight
When the rays of light have not yet met before touching the back of the retina
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Moment
The turning effect of a force
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Centre of mass
Where the weight of and object is concentrated at one point
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