Learning Goals Learn how the human eye works and the common problems with our eyes Learn about various lens technologies Video The Human Eye The Human Eye The Human Eye Lens ability to refract light and allow the eye to focus ID: 784897
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Slide1
12.3 Lens Technologies and the Human Eye
Slide2Learning Goals
Learn how the human eye works and the common problems with our eyes
Learn about various lens technologies
Slide3Video:
The Human Eye
Slide4The Human Eye
Slide5The Human Eye
Lens
: ability to refract light and allow the eye to focus
Ciliary
Muscle
: changes the shape of the lens
Iris
: coloured part of the eye made of muscle fibres that contract and expand to open and close the pupil.
Pupil
: the part of the eye that light passes through
Optical Nerve
: connects the eye to the brain
Slide6The Human Eye
The
cornea tissue that forms a transparent, curved structure in the front of the eye; refracts light before it enters the eye
The retina a layer of rod and cone cells that respond to light and initiate nerve impulses
Rod cells
are very sensitive to light but cannot distinguish between colours
Cone cells
detect colours
Slide7Colour Blindness
There are three types of
cone cells: blue, green, and red.
The exact physical causes of colour blindness are still being researched but it is believed that colour blindness is usually caused by faulty cones but sometimes by a fault in the pathway from the cone to the brain.
Slide8Recall from your study of lenses that when an object is moved, the image also moves. In the eye, however, the distance between the retina and the lens is always the same. So how do we still see clear images at different distances?
Slide9The Human Eye
Slide10Video:
Vision
Problems
Slide114 Common Vision Problems:
Myopia
Hyperopia
Presbyopia
Astigmatism
Slide12Myopia
Near sightedness
Inability to focus on distant objects
Due to an elongated eyeballImage forms in front of retina
Corrected with glasses or contact lenses with diverging lenses
Slide13Hyperopia
Far sightedness
Inability to focus on nearby objects
Due to short eyeball
Image does not form in front of retina, rays meet after
Corrected with glasses or contacts with converging lenses
Slide14Video:
Myopia and
Hyperopia
Slide15Lenses become stiffCiliary muscles cannot make lenses change shape
Cannot focus on nearby objectsCorrected with glasses (bifocals if they are also near sighted)
Presbyopia
Slide16Blurred/distorted visionDue to incorrectly, oval shaped cornea
Astigmatism
Slide17Video:
Laser Eye Surgery
https://www.youtube.com/watch?v=0V4I2xzwGd4
https://www.youtube.com/watch?v=KDgZZhARLsQ
Slide18Read 12.3Chapter 12 Review Questions:
pg 518 # 8,10,12,13,18
Homework