Science Chapter 10: The Human Eye

Study Notes

The human eye functions like a camera, using a lens system to form images on the retina.
Light enters the eye through the cornea, which is a transparent bulge at the front of the eyeball.
The diameter of the eyeball is approximately 2.3 cm; most refraction occurs at the cornea's outer surface.
The eye lens fine-tunes the focal length for focusing on objects at various distances.
The iris, located behind the cornea, controls the size of the pupil, regulating the amount of light entering the eye.
The eye lens creates an inverted real image on the retina, which contains light-sensitive cells.
These cells convert light into electrical signals sent to the brain via optic nerves; the brain interprets these signals for perception of objects.

The eye lens is made of a fibrous jelly-like material and its curvature can be adjusted by ciliary muscles.
When relaxed, the lens becomes thinner, increasing its focal length, allowing clear vision of distant objects.
When focusing on nearby objects, the ciliary muscles contract, thickening the lens and decreasing focal length.
Accommodation refers to the lens's ability to adjust its focal length; it has a minimum limit for focus.
The least distance of distinct vision, or near point, is about 25 cm for a young adult with normal vision.
The far point is infinity for a normal eye, meaning clear vision is possible from 25 cm to infinity.
Cataracts occur when the lens becomes cloudy, causing vision loss, which can be treated with surgery.

Refractive defects of the eye can lead to blurred vision and difficulty in focusing on objects.
Common refractive defects include myopia (nearsightedness), hyperopia (farsightedness), and astigmatism.
Glasses or contact lenses are used to correct these vision defects, allowing light to focus correctly on the retina.

The human eye functions like a camera, using a lens system to form images on the retina.
Light enters the eye through the cornea, which is a transparent bulge at the front of the eyeball.
The diameter of the eyeball is approximately 2.3 cm; most refraction occurs at the cornea's outer surface.
The eye lens fine-tunes the focal length for focusing on objects at various distances.
The iris, located behind the cornea, controls the size of the pupil, regulating the amount of light entering the eye.
The eye lens creates an inverted real image on the retina, which contains light-sensitive cells.
These cells convert light into electrical signals sent to the brain via optic nerves; the brain interprets these signals for perception of objects.

The eye lens is made of a fibrous jelly-like material and its curvature can be adjusted by ciliary muscles.
When relaxed, the lens becomes thinner, increasing its focal length, allowing clear vision of distant objects.
When focusing on nearby objects, the ciliary muscles contract, thickening the lens and decreasing focal length.
Accommodation refers to the lens's ability to adjust its focal length; it has a minimum limit for focus.
The least distance of distinct vision, or near point, is about 25 cm for a young adult with normal vision.
The far point is infinity for a normal eye, meaning clear vision is possible from 25 cm to infinity.
Cataracts occur when the lens becomes cloudy, causing vision loss, which can be treated with surgery.

Refractive defects of the eye can lead to blurred vision and difficulty in focusing on objects.
Common refractive defects include myopia (nearsightedness), hyperopia (farsightedness), and astigmatism.
Glasses or contact lenses are used to correct these vision defects, allowing light to focus correctly on the retina.