High frequency, short wavelength, affect photographic film in the same way as light, absorbed by metal and bone, transmitted by healthy tissue
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What can x-rays be used for?
To form images of bones on photographic film to check for fractures and dental problems. Can be used to treat cancer tumors.
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What is a charged coupled device?
A device that forms electronic images of x-rays
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How does a CT scanner work?
A CT scanner uses x-rays to produce digital images of a cross section through the body.
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How can see soft tissue in the body using x-rays?
We can fill soft tissue with a contrast medium that absorbs the X-rays so that they can be seen.
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What happens to light rays passing through a converging lens?
Parallel rays of light that pass through a converging (convex) lens are refracted so that they converge to a point
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What is the point that light rays converge to in a convex lens?
The prinicpal focus or focal point.
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The distance from the centre of the lens to the principal focus is the...
focal length
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Why is there a principal focus on each side of a lens?
Because light can pass through the lens in either direction.
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If an object is further away from a lens than the principal focus, what type of image is formed?
An inverted, real image.
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How is the size of a image determined?
The size of an image depends on te position of the object. The nearer the object is to the lens, the larger the image.
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If an object is nearer to the lens than the principal focus, what type of image is formed?
An upright virtual image is formed behind the object. The image is magnified - the lens acts as a magnifying glass.
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How can we calculate the magnification of an image?
Dividing image height by object height. The units cancel out so there is not unit.
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What happens to rays of light passing through a diverging lens?
Paralled rays of light passing through a diverging lens are refracted so that they diverge away from a point.
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What is another name for a diverging lens?
A concave lens
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What type of image is always formed by a diverging lens?
Virtual image
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How can a converging lens be made to produce a virtual image?
If the object is nearer to the lens than the focal point.
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Tell me about endoscopes.
Endoscopes are devices use to look inside the body without cutting it open or performing keyhole surgery. It contains bundles of optical fibres which are thin flexible glass fibres. Light rays are sent along the fibres using total internal reflection
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Why are optical fibres used in endoscopes instead of other materials?
Because total internal reflection can only take place when a ray travels from a more dense to a less dense material and optical fibres are made from glass which is more dense.
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What is the critical angle?
The critical angle is the angle of incidence that causes light to refracted along the boundary
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What three constructions lines must we draw on a ray diagram to find the corresponding image?
1. 1st ray parallel to the axis is refracted through F 2. 2nd ray passes straight through the centre of the lens Ray 3 passes through F and is refracted parallel to the axis.
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Is the image formed in a camera virtual or real?
A camera uses a converging lens to form a real image of an object on a film or an array of CCDs.
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What is a near point? What is the human eye's near point?
The nearest point to an eye at which the object can be seen in focus by the eye. For the human eyes it 25cm from the eye.
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What is the far point of an eye?
Infinity
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How can we work out the power of a lens? What is it?
Divide 1 by focal length of the lens in metres.
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What part of the eye focus the light onto the retina?
The cornea and eye lens
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What part of the eye changes the thickness of the eye lens?
The ciliary muscles- attached to the lens by suspensory ligaments.
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Other cards in this set
Card 2
Front
What can x-rays be used for?
Back
To form images of bones on photographic film to check for fractures and dental problems. Can be used to treat cancer tumors.
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