Want to see correct answers?
Login or join for free!
Question Group Info

This question group is public and is used in 2 tests.

Author: Lovinmuzic
No. Questions: 7
Created: Mar 31, 2011
Last Modified: 9 years ago

Seeing in Stereo

View group questions.

To print this group, add it to a test.

1 Have you ever asked yourself why you have two eyes instead of one, three, or even hundreds as some insects have? Have you wondered why your eyes are set close together on the front of your face rather than on the sides of your head, as on animals like rabbits, antelopes, and horses? The reasons are simple and important to the way you see the rest of your world.

2 Your eyes are like two small cameras. A camera captures an image of an object and records this image in miniature on a small piece of film. Similarly, when you look at something, each eye takes in what it sees and sends this image to the back of the eyeball. From each eye, an optic nerve then sends the image to the brain. Because your eyes are set close together, they view the world from about the same height but from slightly different angles. While your right eye sees an object a little to the right, your left eye sees the same object slightly to the left. Working as a team, the eyes send the images to the part of your brain called the cerebral cortex, which assembles them into a single, centered image.

3 Seeing with two eyes working together is called stereoscopic vision. This allows you to view the world in three dimensions, or 3-D. These dimensions are height, width, and depth. Perceiving depth allows you to judge the distance between you and the objects you see. It also helps you to adjust to the changing angle at which you see something as you move closer to or farther away from it. As you walk along a sidewalk, for example, seeing in stereo helps you to know how close you are to the street, how far you need to walk to arrive at a certain building, and how close you are to stepping on a rock or a piece of glass. As your body moves, your eyes give you a continual flow of information about where things are in relation to where you are.

4 If images are coming from only one eye, however, only two of these dimensions?height and width can be perceived. A world seen with one eye is thus two-dimensional, as in a photograph. Depth perception is lacking, making it more difficult to move around safely.

5 Now consider why your two eyes are located on the front of your face. Think of other animals with this same arrangement. Some examples are lions, wolves, and owls. What do these creatures have in common? They are all animals that hunt. These animals have eyes facing directly in front of them. This provides a field of vision that is about 180 degrees wide, like a half-circle. This kind of sight is called binocular vision.

6 On the other hand, animals that are hunted have eyes on the sides of the head. This provides nearly a 360-degree field of vision. Because these animals need to be on the alert in order to stay alive, they need to see things coming from the sides and from behind. However, without stereoscopic vision, these animals have a more difficult time determining how far away a threat is.

7 With vision that is both stereoscopic and binocular, humans share with predators the ability to see clearly from side to side and to accurately determine how far away objects are. If you think it would be great to have another type of vision, perhaps with hundreds of tiny eyes like many insects do, think again! Each tiny insect eye sees only a tiny part of what the creature is viewing. Besides, what if you needed glasses? Be glad for the eyesight that you have.
Grade 8 Reading Strategies CCSS: CCRA.R.8, RI.8.8
The author of this passage concludes that "seeing in stereo":
  1. helps people to have better vision than animals have
  2. would be better if it allowed for a wider field of vision
  3. is an ability humans are fortunate to have
  4. is similar to the way cameras work
Grade 7 Reading Strategies
This article would most likely be found in a
  1. textbook about animal behavior.
  2. popular science or health magazine
  3. newspaper?s local news section
  4. professional journal for eye doctors
Grade 7 Reading Strategies
Grade 7 Reading Strategies
Stereoscopic vision is a result of having
  1. hundreds of eyes, all seeing parts of an image.
  2. two eyes close to one another that work.
  3. a three-hundred-sixty-degree field of vision.
  4. one eye on either side of the head, each seeing a different image.
Grade 7 Reading Strategies
According to this passage, an eye is like a camera because both
  1. have an optic nerve
  2. are able to perceive color
  3. record images in miniature
  4. work only while remaining still
Grade 8 Reading Strategies CCSS: CCRA.R.8, RI.8.8
Which claim from the article is least supported by factual evidence?
  1. Your eyes are like two small cameras
  2. This allows you to view the world in three dimensions, or 3-D.
  3. On the other hand, animals that are hunted have eyes on the sides of the head
  4. If you think it would be great to have another type of vision . . . think again!