Question

We see images in three dimensions because a. our lenses can change shape. b. rods are in one eye and cones are in the other. c. our eyes are positioned slightly apart. d. our retinas are curved.

Short answer

Option C: our eyes are positioned slightly apart.

Step-by-step solution

Understand the Question

The question is asking for the reason why we see images in three dimensions (3D). Consider aspects of our vision and biology that contribute to depth perception.

Analyze Each Option

Let’s break down each answer choice to determine which best explains 3D vision.

Evaluate Option A

Option A states that our lenses can change shape. This is true, but it mainly affects our ability to focus on objects at various distances, not necessarily 3D vision.

Evaluate Option B

Option B says that rods are in one eye and cones are in the other. This is incorrect; both types of photoreceptors are present in both eyes and are related to light detection and color vision.

Evaluate Option C

Option C states that our eyes are positioned slightly apart. This is correct because the slight difference in the angle from which each eye views an object contributes to depth perception, creating a 3D image.

Evaluate Option D

Option D suggests that our retinas are curved. While this is true, it is not the primary reason for 3D vision. Curved retinas do help with forming images, but they do not directly account for depth perception.

Determine the Correct Answer

Based on the evaluation, the correct answer is option C. Depth perception and 3D vision are primarily a result of our eyes being slightly apart, giving us binocular vision.

Key concepts

Depth Perception

Depth perception is the ability to judge the distance of objects and see the world in three dimensions. This crucial aspect of human vision allows us to perform everyday activities like driving, playing sports, and even walking without bumping into things. Depth perception relies on several visual cues:

• Binocular Cues: These are visual information taken in by both eyes. The slight difference in view between each eye, known as binocular disparity, helps in judging distance.


• Monocular Cues: These can be observed with just one eye and include things like size, texture gradient, interposition (when one object overlaps another), and linear perspective (parallel lines appearing to converge).

Good depth perception comes from the brain's ability to integrate these cues. Without it, activities like catching a ball or parking a car would be incredibly challenging.

Binocular Vision

Binocular vision is a type of vision where two eyes work together to create a single, cohesive image. This is essential for depth perception and is made possible by the eyes' placement and how they take in visual information. Both eyes view the same scene from slightly different angles because they are positioned a few centimeters apart on the face. This slight difference is known as binocular disparity.

The brain uses this disparity to calculate the distance to various objects. Here's how it works:

• Convergence: When you look at objects that are close, your eyes turn inward slightly. This turning is greater for closer objects and minimal for distant ones.


• Stereopsis: This is the process by which the brain combines the two slightly different images from each eye into one image, creating the perception of depth.

People with only one functional eye lack this type of depth perception, though they can still judge distance using monocular cues.

Human Vision

Human vision is an incredibly complex process involving multiple parts of the eye and brain. Each eye captures light and converts it into electrical signals, which the brain interprets as images. This process relies on components like:

• Cornea: The transparent front part of the eye that helps to focus incoming light.


• Lens: Adjusts its shape to help focus light on the retina, aiding in seeing objects at different distances.


• Retina: Contains photoreceptors (rods and cones) that detect light and color.


• Optic Nerve: Transmits visual information from the retina to the brain.

The brain processes these signals to form images, allowing us to see the world around us. Our ability to see in three dimensions primarily depends on binocular vision, with each eye providing slightly different images that are combined in the brain to create depth. This sophisticated system allows us to navigate and interact with our environment effectively.