SNC2D – Ms. Venables
The Eye!
Instructions: Use pg 572-576 of your textbook to fill out following note. This handout will be your notes for this
topic and it will be on the unit test on Friday May 30th.
PARTS OF THE EYE
1. Label the parts of the eye in the diagram below. If you have time colour the diagram.
2. Fill in the structures of the eye you identified in 1) and then describe the function of that part.
Structure
A)Cornea
Description/Function
-Transparent bulge on top of the pupil that focuses light
-Light refracts more here than through the lens
B)Pupil
-Hole where light enters the eye
C)Iris
-Coloured part of the eye
-opens and closes around the pupil to let more or less light in
D)Lens
-causes light to converge (focus)
E)Retina
-Contains light sensitive cells that convert the light signal into
an electrical signal
F)Optic Nerve
-Carries the electrical signal created by your retina to the brain
HOW WE SEE!
3. Draw a ray diagram of an image form on our eye and then fill in the blanks below.

The cornea-lens combination of our eye acts like a CONVERGING lens.
 Describe the image characteristics:
o Location: IN FRONT (opposite side as object)
Orientation: INVERTED
o Size: SMALLER
Type: REAL
 Electrical impulses from the RETINA travel through the OPTIC NERVE to the brain where we “see”
the image.
 The brain takes the INVERTED image from the retina and FLIPS it so that the image we “see” appears
UPRIGHT
EYE ACCOMODATION


In human eyes, CILIARY muscles help the eye focus on distant and nearby objects by slightly changing the
SHAPE of the eye lens.
The change in shape of the eye lens changes the FOCAL length of the lens to allow focusing of the image
on the RETINA.
FOCUSING PROBLEMS
4. Fill in the table below
Problem
Definition
Far-sighted
Hyperopia
Presbyopia
Myopia
Trouble seeing..
-Can see distant
objects
-Has trouble
seeing objects
nearby
Age-related
vision condition
Has trouble
reading fine print
as they get older
Near-sightedness
-Can see up close
-Has trouble
seeing distant
objects
Caused By..
-distance between
the lens and retina
is too small
-OR because the
cornea-lens
combination is too
weak
-light focuses
BEHIND the
retina
-loss of lens
elasticity
Corrected By..
-converging lens
(positive
meniscus)
Ray Diagram
-converging lens
N/A
-distance between
lens and retina is
too large
-cornea-lens
combination
converges light
-diverging lens
(negative
meniscus)
too strongly
-light focuses IN
FRONT of the
retina
VIDEO: https://www.youtube.com/watch?v=gvozcv8pS3c
5. HOMEWORK: Complete the following questions on a separate piece of paper p.577 #1-5
1. Describe at least three similarities between a camera and a human eye.
Camera
Eye
Function
diaphragm
iris
Controls amount of light
entering
Aperture
Pupil
Hole where light enters
Converging lens
Lens and Cornea
Refract light to converge to
form a sharp image
Film or digital sensor
Retina
Converts light into an electrical
signal
2. The text states that we actually “see with our brain.” What is meant by this?
The eyes simply capture the light, the brain is what processes the information.
3. a) What is the difference between far-sightedness and near-sightedness?
Far-sighted (hyperopia): can see distance but not up close, image focused past retina
Near-sighted (myopia): can see up close but not distance, image focused closer than retina
b) What simple lens shape would correct each of these problems?
Far-sighted  converging lens (positive meniscus)
Near-sighted  diverging lens (negative meniscus)
4. The actual lens shape to correct the two vision problems of far-sightedness and nearsightedness have been modified.
a) what are these new lens shapes called? Draw an example of each new shape.
Positive meniscus and negative mensicus
b) Why have they been changed from the basic lens shapes?
More cosmetically appealing than the thick shape of a basic lens