This photo shows a pair of eyeglasses. The part of the image that is seen through the lens is in focus while everything outside of the lens frame is out of focus.
The human eye is a fascinating organ. There are many parts of the eye that aid in allowing a person to see, but this paper will talk only the components that allow images to form on the retina. In general, the ciliary muscle can relax or contract to adjust the focal length of the lens. When the muscle is contracted, the curvature of the lens increases, thereby decreasing the focal length of the lens. When the muscle is not contracted, the curvature of the lens is decreased and the focal length of the lens is extended (Cutnell and Johnson 2012). This is how people are able to focus on objects at various distances away.
In general, the distance between the lens and the retina (di) is fixed, but the distance to various objects (do) changes. The thin lens and mirror equation can be used to determine focal length, distance to the object, or the distance to the image formed.
1/f=1/d_o +1/d_i
For example, if the distance …show more content…
Different types of lenses cause light to react differently, but in each case, light will bend “toward the thickest portion” of the lens (Broten, 2000). One kind of lens, a concave lens, has the thinnest part of the lens in the middle and the thickest parts on the outsides. These lenses have a negative focal length and cause light to diverge. The spreading of light away from the center of the lens “moves the focal point forward” (Broten, 2000). Another type of lense, a convex lens, has the thickest part of the lens in the middle and the thinnest part at the outsides. These lenses have a positive focal length and cause light to converge. The bending of the light toward the center of the lens causes the focal point to move back (Broten, 2000). These different lenses can be used to treat myopia and
The human eye is a fascinating organ. There are many parts of the eye that aid in allowing a person to see, but this paper will talk only the components that allow images to form on the retina. In general, the ciliary muscle can relax or contract to adjust the focal length of the lens. When the muscle is contracted, the curvature of the lens increases, thereby decreasing the focal length of the lens. When the muscle is not contracted, the curvature of the lens is decreased and the focal length of the lens is extended (Cutnell and Johnson 2012). This is how people are able to focus on objects at various distances away.
In general, the distance between the lens and the retina (di) is fixed, but the distance to various objects (do) changes. The thin lens and mirror equation can be used to determine focal length, distance to the object, or the distance to the image formed.
1/f=1/d_o +1/d_i
For example, if the distance …show more content…
Different types of lenses cause light to react differently, but in each case, light will bend “toward the thickest portion” of the lens (Broten, 2000). One kind of lens, a concave lens, has the thinnest part of the lens in the middle and the thickest parts on the outsides. These lenses have a negative focal length and cause light to diverge. The spreading of light away from the center of the lens “moves the focal point forward” (Broten, 2000). Another type of lense, a convex lens, has the thickest part of the lens in the middle and the thinnest part at the outsides. These lenses have a positive focal length and cause light to converge. The bending of the light toward the center of the lens causes the focal point to move back (Broten, 2000). These different lenses can be used to treat myopia and