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