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The Eye and the Lens

Grade 5:  Describe the structure and function of the major organs of the nervous system (302-5e)

How the Eye Works


eye diagram web

 We begin the class by looking at a diagram of the eye.  We are going to investigate a few parts of the eye.  The lens and retina are the most important.

Hello Cornea

The cornea is the bulge in front of the lens that allows light to enter.

 Close both eyes and gently place a finger on your eyelid .

 Now without opening your eyes, "look" to the right and left.  As your eye moves you should be able to feel the bump. 

That's your cornea.


Iris Demo

The iris is the coloured part of the eye that controls the amount of light entering the pupil. 

The iris has rings of muscles in it. When the light is bright the muscles make the pupil smaller

Have students sit or stand opposite a partner.

Tell them to watch their partner's iris.

Turn off the classroom lights.

What Happened?   Turn the lights on an off a couple times.

 Watch  what happens


Upside  Down  Image


This easy demonstration was first shown to my class by photographer Peter Barss

Take a magnifying glass or lens and focus an image on a white sheet of paper.

Place paper on table and focus overhead lights on your paper.

Move the lens up and down to focus the light.

The magnifying glass acts like the lens of your eye focusing the light onto the back of your eye... the retina.

The retina has a bunch of nerves called rods and cones that are sensitive to light.


 Turn of the classroom lights and stand by a window. Focus an  outdoor image on your paper.

 You will see that the image is upside down.

You can also focus a candle



Because of the way our eyes work there are a number of illusions that can be demonstrated.

1. Hole in the Hand

Roll up a sheet of paper. Hold it to your right eye.

 Hold your left hand at least 10 cm in front of your left eye.

 Look straight ahead with both eyes and you should see a hole in the middle of your palm.


2. Floating Frankfurter

Hold your index fingers about 12 cm. in front of your eyes.

Wiggle your fingers up and down while you focus your eyes on the other side of the room.


3. Magic Money

Take two coins and grip them between the tips of your index fingers.

 Rub the coins against each other in an up and down motion.  A third coin will appear.




Stereo Vision

Predators like dogs, cats and owls have their eyes placed on the front of the skull.

 This gives them better depth perception.

Herbivores like horses have eyes placed on the sides of the skull so they can detect the motion of a predator.


Test your depth perception.  Take two pencils.

 Hold one in each hand horizontally. 

Close one eye and try to touch the erasers together.

Now try it with both eyes open. 



Web Sites


Here is a page with more info on how a lens works

How the Eye Works  Info from the Exploratorium along with a cow eye dissection.

Not Exactly Rocket Science : Mantis shrimps have a unique way of ...

The Mantis shrimp may have the most  well developed sense of sight in the animal kingdom.

Parts of the Eye

The Blind Spot  Did you Know?... an octopus does not have a blind spot!

Mark Newbold's Animated Necker Cube

Ball catching Experiment

Orion Math:    A subtraction activity with Light Years


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I last edited the page on November 11  2010.


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Last updated: 01/02/13.