The air, Nowhere so clear, sharpened his visual ray.
--Milton.
2. That can be seen; visible. [R.]
{Visual angle}. (Opt.) See under {Angle}.
{Visual cone} (Persp.), a cone whose vertex is at the point
of sight, or the eye.
{Visual plane}, any plane passing through the point of sight.
{Visual point}, the point at which the visual rays unite; the
position of the eye.
{Visual purple} (Physiol.), a photochemical substance, of a
purplish red color, contained in the retina of human eyes
and in the eyes of most animals. It is quickly bleached by
light, passing through the colors, red, orange, and
yellow, and then disappearing. Also called {rhodopsin},
and {vision purple}. See {Optography}.
{Visual ray}, a line from the eye, or point of sight.
{Visual white} (Physiol.), the final product in the action of
light on visual purple. It is reconverted into visual
purple by the regenerating action of the choroidal
epithelium.
{Visual yellow} (Physiol.), a product intermediate between
visual purple and visual white, formed in the
photochemical action of light on visual purple.