Chapter 2 Section 4 Seeing Light

Vision Your eyes sense light When light from an object enters your eye, your eye sends a signal to your brain and you see the object

Vision Cont’d

Vision cont’d Light enters the eye Light enters the eye through the transparent front surface called the cornea. Cornea protects the eye. Then, light enters the pupil, the part of the eye that looks black Pupil is an opening through which light enters the inside of the eye.

Vision cont’d The iris is a ring of muscle that contracts and expands to change the size of the pupil. The iris gives the eye its color.

Vision cont’d An Image forms: After entering the pupil, the light passes through the lens The lens bends the light to form an upside down image on the retina The retina is a layer of cells that lines the inside of the eyeball

Vision cont’d Retina: Made up of tiny, light-sensitive cells called rods and cones. Rods contain a pigment that responds to small amounts of light Cones respond to color

Vision cont’d Correcting vision If the eyeball is slightly too long or too short, the image on the retina is out of focus. Can be fixed by wearing glasses, contact lenses, or having a lasik surgery

Vision cont’d Nearsighted : can see nearby things clearly, but objects at a distance are blurred. The eyeball is too long, so the lens focuses the image in front of the retina Farsighted : can see distant objects clearly, but nearby objects appear blurry. The eyeball is too short, so the image that falls on the retina is out of focus