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Lenses
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Slide 1

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Health

Convex lenses bring rays to a focus.The more curved the lens , the quicker the rays are focussed.

Concave lenses make rays spread out.The more curved the lens ,the more the rays spread out.

Slide 2

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HEALTH

Long sighted people can only focus on far away objects.The eye behaves normally.When viewing nearby objects ,the lens brings the rays of light to a focus beyond the retina.

Slide 3

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HEALTH

This is rectified by putting a convex lens in front of the eye.

Slide 4

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HEALTH

Short sighted people can only focus on nearby objects.The eye works normally.

With nearby objects, the lens brings the rays to a focus before the retina.This is corrected by putting a concave lens in front of the eye.

Slide 5

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HEALTH

The focal length of a lens is the length from the middle of the lens where the rays come to a focus.

Fibre optical cables are cold light sources because no heat energy is produced in them.

Slide 6

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HEALTH

An endoscope consists of two bundles of optical fibres.The first takes light down inside a patients body to illuminate a source of concern.The second takes light to the surgeon`s eye via a lens and camera.

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