2. A combination of two or more such pieces, sometimes with other optical devices such as prisms, used to form an image for viewing or photographing. Also called "compound lens".
3. A device that causes radiation other than light to converge or diverge by an action analogous to that of an optical lens.
4. A transparent, biconvex body of the eye between the iris and the vitreous humor that focuses light rays entering through the pupil of the eye to form an image on the retina.
5. The transparent part of the eye, behind the pupil.
The lens was named after the lentil bean because it resembled it in shape and size
A lens is the transparent structure inside the eye that focuses light rays onto the retina which is the nerve layer that lines the back of the eye, senses light and creates impulses that go through the optic nerve to the brain.
In addition to the lens, the eye has a number of other components including the cornea, iris, pupil, retina, macula, optic nerve, and vitreous.
- The cornea is the clear front window of the eye that transmits and focuses light into the eye.
- The iris is the colored part of the eye that helps regulate the amount of light that enters the eye.
- The pupil is the dark aperture in the iris that determines how much light is let into the eye.
- The retina is the nerve layer that lines the back of the eye, senses light and creates impulses that travel through the optic nerve to the brain.
- The macula is a small area in the retina that contains special light-sensitive cells and allows us to see fine details clearly.
- The optic nerve is the nerve that connects the eye to the brain and carries the impulses formed by the retina to the visual cortex of the brain.
- The vitreous humor is a clear, jelly-like substance that fills the middle of the eye.
Other bifocal lenses are the flat-top Franklin type, or blended invisibly.
2. A lens whose power increases continuously and regularly in a downward direction, avoiding the discontinuity of bifocal and trifocal lenses.