The Human Eye: Structure and Function

Retina

Cornea

2.3 cm

<p>Pupil</p> Signup and view all the answers

<p>Finer adjustment of focal length</p> Signup and view all the answers

<p>Iris</p> Signup and view all the answers

<p>Sight/Vision</p> Signup and view all the answers

<p>Cornea</p> Signup and view all the answers

<p>A Camera</p> Signup and view all the answers

<p>Cornea</p> Signup and view all the answers

<p>Both use a lens to focus an image on a light-sensitive surface; the eye uses the retina, while a camera uses film or a digital sensor. Both also have an aperture to control the amount of light entering.</p> Signup and view all the answers

<p>The cornea has a greater difference in refractive index compared to the air than the lens does compared to the surrounding fluids in the eye, resulting in more significant bending of light.</p> Signup and view all the answers

<p>The iris is a muscular diaphragm that adjusts the size of the pupil. It contracts to decrease the pupil size in bright light, reducing the amount of light entering, and dilates to enlarge the pupil size in dim light, increasing the amount of light entering.</p> Signup and view all the answers

<p>The crystalline lens changes its shape, becoming thicker to focus on nearby objects and thinner to focus on distant objects. This adjustment of focal length is called accommodation.</p> Signup and view all the answers

<p>For clear vision, the light rays must converge precisely on the retina. If the image forms in front of or behind the retina, the light rays will not be focused when they reach the retina, resulting in a blurred image.</p> Signup and view all the answers

<p>Color perception helps us differentiate objects, assess ripeness of fruits, and interpret warning signs. It is crucial in distinguishing between different objects and understanding their properties.</p> Signup and view all the answers

<p>In dim light, the iris dilates to allow more light to enter the eye, and the retina's sensitivity increases through biochemical adjustments. These changes are automatic and take time to fully adjust.</p> Signup and view all the answers

<p>If the cornea was not transparent, light would be scattered or blocked, preventing a clear image from being formed on the retina, resulting in blurry or no vision.</p> Signup and view all the answers

<p>Binocular vision provides depth perception, allowing us to judge distances accurately. It also increases the field of view and provides a backup in case one eye is injured.</p> Signup and view all the answers

<p>Light first enters through the cornea, where most of the refraction occurs. It then passes through the pupil, controlled by the iris, and is further focused by the crystalline lens onto the retina, where the image is formed.</p> Signup and view all the answers

<p>The iris adjusts the size of the pupil to regulate the amount of light entering the eye. In bright light, the iris contracts the pupil to reduce light intake, while in dim light, the iris dilates the pupil to allow more light in, optimizing vision under different conditions.</p> Signup and view all the answers

<p>Accommodation is the process by which the eye adjusts its focal length to see objects at different distances. The ciliary muscles change the shape of the lens; to focus on nearby objects the muscles contract, making the lens thicker and more curved, increasing its refractive power.</p> Signup and view all the answers

<p>Most of the refraction occurs at the cornea because of the large difference in refractive indices between air and the cornea material. The crystalline lens provides finer adjustments of focal length and is required to accurately focus objects at varying distances on the retina. The lens provides about 20% of the focusing power.</p> Signup and view all the answers

<p>The diameter of the eyeball is important because it determines the distance between the lens and the retina. This distance affects the focusing of light. Variations from the normal diameter can lead to refractive errors like myopia or hyperopia.</p> Signup and view all the answers

<p>The retina contains photoreceptor cells (rods and cones) that convert light into electrical signals. Rods are sensitive to low light and responsible for black and white vision, while cones are responsible for color vision and function in brighter light. These signals are then processed by other retinal neurons and sent to the brain via the optic nerve.</p> Signup and view all the answers

<p>The cornea and lens system of the eye are analogous to the camera lens, focusing light. The iris is analogous to the camera's diaphragm, controlling the amount of light entering. The retina is analogous to the camera's sensor, capturing the image.</p> Signup and view all the answers

<p>Binocular vision allows for depth perception (stereopsis) because each eye sees a slightly different view, enabling the brain to judge distances accurately. It also expands the field of view and provides a 'spare' in case one eye is damaged.</p> Signup and view all the answers

<p>The focal length of the eye lens changes through the action of the ciliary muscles, which alter the curvature of the lens. When viewing distant objects, the ciliary muscles relax, flattening the lens and increasing the focal length. When viewing near objects, the ciliary muscles contract, thickening the lens and decreasing the focal length, this process ensures that the image from the eye is always focused sharply on the retina, regardless of the object’s distance.</p> Signup and view all the answers

<p>If the cornea were not transparent, light would be scattered or blocked, causing blurred vision or blindness. Transparency is essential for allowing light to pass through and be properly refracted by the lens onto the retina. Scarring or clouding of the cornea directly impairs light transmission.</p> Signup and view all the answers

<p>Rods function in low light, providing black-and-white vision and are responsible for peripheral vision and night vision, while cones function in bright light. Cones provide color vision and enable high visual acuity. Rods are more sensitive to light but do not percieve colour.</p> Signup and view all the answers

A sensitive organ that enables vision by processing light.

The transparent structure that focuses light onto the retina.

A light-sensitive screen at the back of the eye that receives images.

A transparent bulge at the front of the eyeball that refracts light.

The colored part of the eye that controls the size of the pupil.

The adjustable opening in the center of the iris that lets light in.

The distance needed for the lens to focus light on the retina.

The bending of light as it passes through different mediums.

Visual effects produced by the interaction of light with matter.

Eyewear that uses lenses to correct vision defects.

The human eyeball is approximately spherical, measuring about 2.3 cm in diameter.

The cornea refracts light and forms a bulge on the eye's front surface.

The retina is the light-sensitive screen that receives images formed by the lens.

The iris is a muscular diaphragm that controls the size of the pupil, regulating light intake.

The pupil is the opening that determines how much light enters the eye.

The crystalline lens fine-tunes the focal length for focusing on the retina.

Refraction is the bending of light as it passes through different media, mainly the cornea.

The human eye is the most sensitive organ, allowing color and detail perception.

Spectacles use lenses to correct defects in vision by adjusting light focus.

Enables vision by processing light information from surroundings.

The human eyeball is approximately spherical, about 2.3 cm in diameter.

The cornea is the transparent front part that refracts light entering the eye.

Iris controls the size of the pupil to regulate light intake.

Crystalline lens fine-tunes the focal length for clearer vision at various distances.

The eye forms images on the retina, which is light-sensitive.

Most refraction occurs at the outer surface of the cornea.

The human eye is sensitive, allowing perception of colors and details.