The Blind Spot One of the most dramatic experiments to perform is the demonstration of the blind spot.
The blind spot is the area on the retina without receptors that respond to light. Therefore an image that falls on this region will NOT be seen. It is in this region that the optic nerve lookijg the eye on its way to the brain. To find your blind spot, look at the image below or draw it on fuj piece of paper:. Close your right eye. Hold the image or place your head from the computer monitor about 20 inches away. At a certain distance, the dot will disappear from sight Reverse the process.
Close your left eye and look at the dot with your right eye. Here are some more images that will help you find your blind spot. For this image, close your right eye. With your left eye, look at the red circle. Slowly move your head closer to the image. At a certain distance, the blue line will not look broken!!
This is because your brain is "filling in" the missing information. This next image allows you to see another way your brain fills in lookibg blind spot. Again, close your right eye. The space in the middle of the vertical lines will disappear. In the next two images, again close your right eye. With your left eye, look at the s on the right side, starting with the "1.
Keep your head still, and with your left eye, look at the other s. The sad face should disappear when you get to "4" and reappear at about "7. You should see the red dot in your peripheral vision. The red dot will move vor the left to the right and disappear and reappear as the dot moves into and out of your blind spot.
Materials: Blind spot testers: make your own or download a template of 11 testers. More lots more about Blind Spots Read about the eye.
Calculate the Diameter of Your Blind Spot. An octopus does not have a blind spot! The retina of the octopus is ffor more logically than the mammalian retina. The photoreceptors in the octopus retina are located in the inner portion of the eye and the cells that carry information to the brain are located in the outer portion of the retina. Therefore, the octopus optic nerve does not interrupt any space of retina. Octopus Eye Image courtesy of Biodidac. Make colors appear using only black and white!
Make your own Benham Disk. Depth Perception - I For grades K Two eyes are ,ooking than one, especially when it comes to depth perception. Depth perception is the ability to judge objects that are nearer or farther than others.
To demonstrate the difference of using one vs. Hold them either vertically or horizontally facing each other at arms-length from your body. With one eye closed, try to touch the end of the pencils together.
Now try with two eyes: it should be much easier. This is because each eye looks at the image from a different angle. This experiment can also be done with your fingers, but pencils make the effect a bit more dramatic. Materials: Pencils but your fingers make a good substitute. Drop IT! Collect a set of pennies or buttons or paper clips. Sit at a table with your subject.
Put a cup in front of your subject. The cup should be about two feet away from the subject.
Hold a penny in the air about 1. Move the penny around slowly.
Ask your subject to say "Drop it! When the subject says "Drop it," drop the penny and see if it makes it into the cup. Try it again when the subject uses both eyes.
Try it again with the cup farther lolking from the subject. Try it again with the cup closer to the subject. Compare the of "10 drops" at each distance. Questions: Is there improvement with two eyes? Is there improvement with the cup is closer to the subject? The actual dimensions of the circles are not too important and you don't have to color the circles.
Place the target on the ground about five feet in front of you. Have a friend stand near the target.
Have your friend hold out an ink marker with the tip pointing down. Close one eye.
Tell your friend to move forward or backward or side to side until you think the marker would hit the center of the target if it was dropped. Tell your friend to drop the marker when you think the marker is over the target center. The marker should leave a spot where it hit the target. Try it 10 times with one eye closed and add up the "score" for the 10 drops.
Now try it with both eyes opened get a different color marker when you use 2 eyes to see the difference on the target. Is your score better when you use two eyes?
Materials: Paper for target Markers two colors. Shifting Backgrounds, Shifting Images For grades K Here's another way to demonstrate how different images are projected on to each eye. Look at an object in the distance feet awaysuch as a clock on the wall. Close one eye, hold up your arm and line up your finger with the object. Now without moving your finger or your head, close the opened eye and open the closed eye. The object in the distance will appear to jump to the side This shows that different images fall on each eye.
Materials: NONE. Dark Adaptation For grades There jhst two types of photoreceptors in the eye: rods and cones. The rods are responsible for vision in dim light conditions, the cones are for color vision. To demonstrate how the photoreceptors "adapt" to low light conditions, get a collection of objects that look slightly different: for example get 10 coke bottle caps, 10 soda bottle caps, and 10 water bottle caps. They should feel the same, but not look the same.
In a bright room, ask students to separate the caps into piles of similar caps. Then turn off the lights so the room is very, very dim. Ask them to separate the caps again. Turn off the lights and look at the Count the of errors. The technical explanation for dark fro is not necessary for small children. Plan to talk and discuss for about minutes After the discussion minutesask the students to separate the caps again in the same very, very dim conditions as before. There should be fewer errors this time because the photoreceptors have adapted to the low light conditions.
Materials: Three sets of bottle caps or other similar items. Visual Illusions Grades Many of these illusions are available as interactive shockwave games in the Neuroscience for Kids Gallery of Visual Illusions.
What you see is not always what is there. Or is it?
The eye can play tricks on the brain. Here are several illusions that demonstrate this point. Lookin Magic Cube Look at the center cube. What side is the front?