Unable to see close objects clearly.

The opening in the diaphragm of a camera; can let more light reach the film by opening wider.

A light-sensitive area at the back of the eye.

The lens commonly used to correct near-sighted vision.

(Of the eye) the shortest distance at which an object is in focus.

In a camera or microscope, a device that controls the amount of light that enters.

The clear covering over the eye.

A lens that is thicker around the middle than around the edges; causes refracting rays to come together.

In optics, the position of an image in relation to the object it reflects.

In a camera this photosensitive material captures the light and creates an image.

The point where the optic nerve enters the retina; has no light-sensing cells.

To bring rays of light to a point.

The natural adjustment in the eye's pupil size in response to varying light levels.

In a camera, a device that open the aperture to allow light to reach the film.

Adjusts the thickness of the lens to focus near or far objects.

A telescope having a convex lens to collect and focus light from a distant object, and an eyepiece to magnify the image.

The process of changing the shape of the lens (in the eye) to adjust for different distances from an object being viewed.

Adjusts the distance between the lens and the film to focus near or far objects.

Fluid between the iris and the cornea; keeps the eyeball rigid and refracts light.

In binoculars, glass blocks serving as plane mirrors; allow binoculars to be made shorter than telescopes.